Yes, but I would be instantly aware that a large part of the park would have to be demolished to make room for it. And I would be right.
They're already eating a GIGANTIC portion of the theme park property for this IP. Diagon Alley, combined with the Gringotts addition is gigantic. It works for USF solely because of the two park scheme. Not to get cynical but it's just a way Universal can pretty much force a park hopper on the guest. To experience one of the attractions in this new expansion you have to have a park hopper. How brilliant is that?
USH is very small. We should be lucky we're getting a slice of Potter over here, even if by the time it arrives it'll seem a tad old hat. But that's only to theme park nerds. The GP will eat it up. The possibility of Diagon Alley is so far down the line that the possibility would require a number of things to happen and that could take literal decades. It's not worth losing sleep over. Let USF have their money-squeezing expansion.
I mean, god forbid Universal does a Potter phase 3 where you have the option of taking Hogwarts Express to another themed area outside both parks which costs an additional charge. I wouldn't put it past them (because the Potter nuts would fork their money over in a heartbeat), and then everybody would be crying for that to be in CA too even if we GOT Diagon Alley.