While I wouldn't mind it at all it would be a strange decision for him. Go from being the main striker at Dortmund to backup at Barca?
Can't he play on the wings as well?
And tbh, in which big club he'd be a starter right now?
City have Haaland and Alvarez. L'pool just bought Gakpo after spending 100m on Darwin so they're probably out of the race. United could offer him wages and first team minutes but would he really want to go there considering they're far from a guaranteed CL team in near future (which he probably wants). Chelsea is collecting talents from around the world so could add another one and they actually need a striker so if I'd have to guess he'll probably go there.
Can always go to Bayern as most young German talents but his wage demands could be too high for them (but then again this is also even more true for Barca). Or for all we know Perez could sign him just because he can and teenagers are seemingly only ones he's signing these days.
I think he could actually be attracted to Barca (more so if he's really our fan but ofc we know players don't always sign for the clubs they're supposed fans of) given how many minutes we've given to youngsters in recent years. Finances are problematic though. Would he accept being paid in the range of likes of Pedri, Gavi and Araujo and does he really deserve that is another question.
Personally I think it would be the best for his development to stay in Dortmund for a year or two more but looks like he has decided to leave.