Where did you hear about them "getting back into it?" Jimmy doesn't believe it. He probably just meant that the chemistry together would still be there, and that they wouldn't miss a beat if they ever (hypothetically) did do anything.
They'd be making a big mistake to go on TV again. But the theater would be perfect because their ages wouldn't show on stage (their characters could still pass for mid-thirtyish to a distant audience, and hopefully, it wouldn't be captured forever in time on film. But they'd be better off doing new material in the same style, rather than previous scenes. They could never capture all of the classic moments the same again. They'd have to pick up right where they left off as if it were 1998 (no growing up or maturing BS). Even if it did bomb in the theaters... it wouldn't ruin the legacy of the show at all.
If they are considering getting back into it, it's now or never... they don't have too much longer to be able to pull it off, and it's already too late for TV. (IJHO)