With Shamrock around Oda has 0 excuses, time for Blackbeard to kill the Gary Stu
I still think this cant happen until Luffy and Shanks at least reunite or see each other during the fight for One Piece.
The problem with Shanks vs Blackbeard occuring without Luffy will always have the same 2 issues, justifying his win on or off panel. Off panel means all that hype behind Shanks disappears because he was offscreened. On panel would need, what? 10, 20, 30 chapters of buildup and fighting to make all 10 of Shanks' crew to lose?
I definitely expect itll happen, but I expect it in a bigger war while Luffy is distracted with someone else (Akainu?) and Blackbeard takes advantage of a bigger situation that allows him to isolate Shanks or have his crew defeated on panel.
The key for him winning needs to he on the page and IMO it cant happen without being in front of Luffy (it also justifies Luffy taking down Blackbeard further if Shanks and Garp kick the bucket for example)