I'm now a believer that each of the SHs will achieve their dreams in the order they arrived on Shabondy after the 2 year time skip. It's a bit odd that Oda put emphasis on the order in which all of them arrived so I don't think he just added it randomly.
1. Zoro - Become the world's strongest swordsman
I know a few folks hate when this is stated lolz but it has to be said :p. Chances are that the person Zoro would be challenging for the title of WSS is Shiryu and not Mihawk. In which case, Zoro achieving his dream first is very feasible as the SHs will have to settle tings with the BB pirates at some point before reaching raftel. In addition, chances are that Zoro will create a black blade or blades during this Wano arc, which will bring him ever so closer to the title of WSS.
2. Franky - To create and travel with a dream ship which would experience countless battles, can overcome extreme hardships and can reach the end of the Grand Line
Franky will have achieved his dream as soon as the SHs touch down on Raftel so him being second is very plausible.
3. Nami - To draw a map of the entire world
Like Franky as soon as the SHs touch down on Raftel she'd have arrived at the last Island to put on her map. She seemingly does this at night according to an SBS IIRC, so the slight delay after Franky make sense and thus her being 3rd.
4. Usopp - To become a brave warrior of the sea
Till recently, I had always though Usopp will achieve his dream on Elbaf given his relationship with the giants (he aspires to be like Dorry & Broggy) and the fact that he's so enthusiastic about going to Elbaf. The ting tho, is that Usopp's dream is a bit hard to quantify. I mean, how do we know Usopp has become a brave warrior of the Sea? ^^" The criteria for this might be the fact that he was able to make it to the ends of the sea experiencing all those fierce battles with the SHs all the whilst being a regular human and the weakest of the bunch but if that's the case Nami's should technically come shortly after ^^". Regardless, it makes sense that Usopp is in the top half.
5. Chopper - to become a doctor that can cure any disease
I still think that like Roger, Luffy is going to contract and incurable disease (i.e. My first guess would be that it'd be as a result of one of Queen's plagues) and I think it'd be pretty poetic if Luffy like Roger is faced with said conundrum towards the end of his journey of conquering the grandline and is seemingly unable to do what Roger also intended to do but couldn't solely due to said disease. However, overcoming all odds, Chopper somehow manages to cure Luffy of said incurable disease. If Chopper is able to achieve something like that, in a sense, he'd have achieved his dream of being able to cure any disease and It wouldn't be weird if he was referred to as a god doctor that can cure any disease solely because of that. So yh, Chopper could achieve this just before the SHs return back from Raftel, or when they are on their way to reverse mountain, before they go on to challenge the WG.
6. Brook - To meet Laboon again
Brook would've achieved this after the SHs conquer the grand line and return back to reverse mountain. So it makes sense that he's in the later half and number 6 just after Chopper and before Sanji, which I will come to in a bit.
7. Sanji - To find All Blue
No matter how you think about it, all blue is connected to the red line, as it separates the 4 seas, a union that would undoubtedly create the phenomenon known as all blue. In addition, said red line is connected to the celestial dragons, as they picked that spot to dwell on for some reason. So it makes sense that Sanji achieves his dream after the SHs return from raftel and during/after the confrontation with the celestial dragons.
8. Robin - To know the true history
Robin being 8 on the list I'm sure has raised a few eyebrows....lolz and tbf, I'm a bit skeptical about this as well but it isn't impossible. Robin would undoubtedly find out about the void century on Raftel but her dream might only truly come to full completion after the SHs encounter with the WG and the Gorosei EoS.
9. Luffy - To become pirate King?
Yes, but that is just a means to an end. What Luffy really want is to become the freest man on the sea, so it makes sense he achieves after dethroning IM (who is seemingly the ruler of the world) and defeating the WG. Plus the man is our protagonist so it makes sense that he achieves his dream last and that the story ends with that ^^