My guess - Wander Franco.
‘22 cover guy
I would say that Ohtani is the obvious choice. Vlad Jr might be my second guess. They are probably two of the most marketable players right now. It could always be a retired legend.
Remember it is less about a player deserving or earning it and more about who SDS thinks will sell copies and who they can get to do promotion for the game pre-release.
I can't see Franco getting it and I really can't see Seager (Posey maybe). I'd be shocked if it was Acuna after being injured last season.
Vlad for the normal edition.
Ohtani for a plus edition.
Buster for a deluxe edition.
If only one, then Vlad.