Why anyone pays attention to utter guesswork is beyond me. We've gone from Cher being cast as Catwoman, to Megan Fox being Catwoman, to Johnny Depp being the Riddler, then him saying no-one's mentioned it to him, but it could be "a fun gig". Most recently the idea of Phillip Seymour Hoffman being the Penguin emerged (I say "emerged" - that's been suggested by people since the dawn of time), seemingly backed up by Michael Caine, but since debunked by PSH himself, saying no-one's mentioned it to him either.
All the while there's been a solitary voice of a WB producer trying to make the point that there's not even a verdict on Christopher Nolan doing another one yet. The Michael Caine comment's the only other angle that's got the hint of reality about it, as in it involves a direct quote from him after talking to a producer who said they're definitely doing another one and suggesting the Depp/Hoffman angle. Even a brief check of the wording though reveals two important facts. One is tha he asked a producer how to top Heath Ledger, and got those two name as a response, which sounds like a random musing rather than anything else. A more important aspect is Caine's comment "I read it in the paper." To be honest it sounds like he's just having fun fuelling the fans of speculation, and who can blame him?
The only near-certainty is that there'll be another Batman film in due course, because after the success of The Dark Knight why wouldn't there be? And while I'm sure ideas are being thrown around, anything official is likely being kept behind closed doors for the moment. I'll go out on a limb though and say if we do end up seeing Cher as Catwoman onscreen I'll eat a gooseberry. Believe me, I HATE gooseberries.