Something I foresaw all the way back in Wano, it is only becoming more and more obvious 
Whilst pre TS its more muddied, post-TS it is much much more clearer, especially Oda's intentions.
1. Luffy is not the Roger of the new era, Shanks is.
Oda started making this distinction all the way in Wano. Off course pre TS there are things that likened him to Roger, but like all things, Oda's ideas change and its extremely obvious, so obvious that we can see his ideas changing real time, but fundamentally, Luffy, a DF using brawler, cannot have been the fruitless sword and gun wielding Roger of the new era, since he now has the Nika fruit, his personality just does not match up at all either. More on that later, but this is where Shanks comes in:
This chapter displayed Oda's intentions most clearly tbh. I mean, assuming the fact that Rogers "bet" on Shanks (giving the hat) wasn't obvious enough. Off course, this legendary panel speaks for itself:
Next, we can also see how similar Shanks and Rogers personality's were, we know that according to Garp, at times when enemies went after Rogers friends, Roger became a "ferocious demon", who became "violent, short-tempered and self-centered" when he got mad. He destroyed a entire army of a nation because they shit talked his friend....
This personality is strikingly similar to Shanks:
He brutally destroys Kid, then is fine with the giants wiping out his harmless, begging for mercy crew who already gave up their poneglyphs and surrendered. Lets keep in mined that Shanks foresaw Kid about to blow up his fleet members who were exceptionally weak and his "friends". Its clear that both Shanks and Roger, whilst easy going normally, became different people when their friends were threatened, people who normally you could say were quite "evil" or morally gray anitheros at a minimum. Shanks is not the goody 2 shoes some people think he is, and with Bart, its become even clearer.
Lets get back to Luffy.
Unlike Roger/Shanks, Luffy's personality differs. I mean, even if you don't count Nika Zoan influence, we saw that after all the things Kaido did to Luffy's friends, he was having fun fighting Kaido.
2. Luffy is not Roger of the new era, he is the Joy Boy of the new era.
3. Fight? Why
First, we will go back to Shanks. From Buggy's flashback, we know that Shanks had the ambition to go to Laugh tale and find the One Piece. But it stopped abruptly. Why? Its currently unknown but I think the reason is because he realised that he would fall short just like Roger did and be unable to do "something"/find the One Piece without Nika fruit awakening. He didn't give up on his dream, he was just waiting for the day. Which is why he resumed going after the One Piece.
The battle for the One Piece will be a battle of ambition and it'll be fought between the Joy boy of the new era and Roger of the new era. Just like Whitebeard-Roger battles, just like Garp-Roger battles, Shanks doesn't need to be a evil bad guy stereotype for Luffy to fight him. Luffy himself thinks so:
Off course the final fight for the One Piece doesn't mean final fight ever. Since final war will come after Luffy becomes the PK and gets the One Piece. But I think the fight for the One Piece will be between the 2 characters who most resemble Joy Boy and Roger, Luffy and Shanks. And it will be a battle of ambition. Also, there are plenty of other in-story reasons to support this. Bartolomeo's defeat being one, for example. We even saw the figurehead of Barts ship being burned down. Despite being on friendly terms with each other, the relationship between Shanks and Luffy is more akin to rivals now, especially since Luffy became a emperor of the sea. Not the stereotypical bad guy v good guy standard recipe all the other One Piece arcs use.
Whilst pre TS its more muddied, post-TS it is much much more clearer, especially Oda's intentions.
1. Luffy is not the Roger of the new era, Shanks is.
Oda started making this distinction all the way in Wano. Off course pre TS there are things that likened him to Roger, but like all things, Oda's ideas change and its extremely obvious, so obvious that we can see his ideas changing real time, but fundamentally, Luffy, a DF using brawler, cannot have been the fruitless sword and gun wielding Roger of the new era, since he now has the Nika fruit, his personality just does not match up at all either. More on that later, but this is where Shanks comes in:
This chapter displayed Oda's intentions most clearly tbh. I mean, assuming the fact that Rogers "bet" on Shanks (giving the hat) wasn't obvious enough. Off course, this legendary panel speaks for itself:
Next, we can also see how similar Shanks and Rogers personality's were, we know that according to Garp, at times when enemies went after Rogers friends, Roger became a "ferocious demon", who became "violent, short-tempered and self-centered" when he got mad. He destroyed a entire army of a nation because they shit talked his friend....
This personality is strikingly similar to Shanks:
He brutally destroys Kid, then is fine with the giants wiping out his harmless, begging for mercy crew who already gave up their poneglyphs and surrendered. Lets keep in mined that Shanks foresaw Kid about to blow up his fleet members who were exceptionally weak and his "friends". Its clear that both Shanks and Roger, whilst easy going normally, became different people when their friends were threatened, people who normally you could say were quite "evil" or morally gray anitheros at a minimum. Shanks is not the goody 2 shoes some people think he is, and with Bart, its become even clearer.
Lets get back to Luffy.
Unlike Roger/Shanks, Luffy's personality differs. I mean, even if you don't count Nika Zoan influence, we saw that after all the things Kaido did to Luffy's friends, he was having fun fighting Kaido.
2. Luffy is not Roger of the new era, he is the Joy Boy of the new era.
3. Fight? Why
First, we will go back to Shanks. From Buggy's flashback, we know that Shanks had the ambition to go to Laugh tale and find the One Piece. But it stopped abruptly. Why? Its currently unknown but I think the reason is because he realised that he would fall short just like Roger did and be unable to do "something"/find the One Piece without Nika fruit awakening. He didn't give up on his dream, he was just waiting for the day. Which is why he resumed going after the One Piece.
The battle for the One Piece will be a battle of ambition and it'll be fought between the Joy boy of the new era and Roger of the new era. Just like Whitebeard-Roger battles, just like Garp-Roger battles, Shanks doesn't need to be a evil bad guy stereotype for Luffy to fight him. Luffy himself thinks so:
Off course the final fight for the One Piece doesn't mean final fight ever. Since final war will come after Luffy becomes the PK and gets the One Piece. But I think the fight for the One Piece will be between the 2 characters who most resemble Joy Boy and Roger, Luffy and Shanks. And it will be a battle of ambition. Also, there are plenty of other in-story reasons to support this. Bartolomeo's defeat being one, for example. We even saw the figurehead of Barts ship being burned down. Despite being on friendly terms with each other, the relationship between Shanks and Luffy is more akin to rivals now, especially since Luffy became a emperor of the sea. Not the stereotypical bad guy v good guy standard recipe all the other One Piece arcs use.
