Welcome to the forum, Butlin Boy!
I've been reading up on these rumours over on DLP.info too. They're... interesting. I'm going to go out on a limb here and say that I personally think that Mickey's Philharmagic will *never* replace CinéMagique *or* Animagique. I've only got a rough understanding of what the attraction's like inside, but I'm pretty sure that it would be very expensive and troublesome to try and fit it into one of those "soundstages". I'm not saying it will never come to WDS, though - I'd actually bet that it'll be there before 2010. Just in a brand new building.
CinéMagique, for a start, is in Production Courtyard. It would make no sense putting Philharmagic here when Animation Courtyard and Toon Studios (much more suitable locations) are right next door. Add to this the fact that CinéMagique is very popular and easily the best thing in WDS at the moment, and I think it's safe.
Animagique... hmm. Whilst I doubt the show will last very long once the 5th anniversary of the park has been and gone, I highly doubt the replacement will be Philharmagic. It's more likely to be a classic Disney live show, like The Legend of the Lion King. The building is designed as a live show theatre, everything they need is already there. It has the backstage area, the computer systems, the stadium seating... it's perfect. It would also be odd to have both Studio 2 and 3 both featuring cinema attractions. The fact that Animagique is a real show with real, live performers is really important - if they replaced it with a cinema screen, then all the live Disney entertainment would be confined to streetmosphere and parades... which doesn't seem right.
Philharmagic doesn't have stadium seating, and it has a massive 3D screen that wraps around the front of the audience. So for a start, it wouldn't work in Studio 3 without them changing the seating. And, because the building was built with the stadium seating in mind (I think the ground of the seating is part of the concrete structure of the building), they'd have to demolish the entire interior of the building. It just wouldn't be worth it.
So yeah - personally I don't think Philharmagic (at least in it's WDW form - they could alter it) will go into Studio 2 or 3.
I wonder where it could go, then? It might fit quite nicely right behind Art of Disney, as part of an extension of Toon Studios... :?