Ofc BB will win in the end.
This dude basically won "thematically" and was the biggest winner from Marineford, a saga with Whitebeard, Marines and Shichibukai in it.
He is a future Antagonist. And Garp is literally a "White" Beard, an old legend but someone who will lose against the future Rocks.
He is the only Bad Guy in the series who gets Powerups as he is being built up even when his saga isnt over yet. I mean Luffy is a Yonko, SHs would destroy most Yonko crews and are like a RHP crew now, thats the type of Achievement that would actually set the stakes in an arc.
Put me in BB's team.