Here's what I say - if people are really tired of one Flash and want another (remember, Barry was "killed" because DC didn't know what to do with him and creative geniuses like Geoff johns weren't employed yet), and I don't think they will so what's the point anyway.... but if they do, and they're gonna do a final fate of the flash story I suggest somethig like this:
Do a condensed Crisis story with Anti Monitor after Flash 2 or 3 (after Barry has discovered the multiverse, met Jay Garrick, et al) in a 2nd or 3dr JLA film and have it end with Barry's "death" and have Wally take over in Flash 4 or something, probably the start of a new trilogy a few years later (like the Spider-Man films). Smart way to do Crisis without pissing off everyone.