had very mixed reviews (but bordering more on the bad side)
Sorry to point this out, but where the hell did you get that info from? I read a LOT of online reviews and magazine reviews and 80% of the reviews have said its better than the first film.
I'm guessing you are a Narnia fan?
Well reviews I have read have just said that it is not anything special. Also the first film had a 75% score at rottentomatoes.com, Prince Caspian has a 66% score (which is admitedly higher than I had first stated) but that is still not that great.
I agree completely that this film was released at a bad time of year BUT if this had been a really good film which had sparked peoples interest it would have done better than it has domestically. We can't simply blame it's release date for it's poor performance, I personally think it's more to do with people just not being that bothered about this film, it's not 'must see' like Iron Man or Indiana have been.
I just don't think Disney are very good with franchises, look how they turned Pirates of the Carribean into an overlong and confusing mess? (3rd film) They just seem to think that massively increasing the films budget will automatically increase the quality (the pirates sequels were rumoured to cost $250 - 300 million each!)
That said I'm sure they could come up with a good attraction for Narnia, the source material is still strong enough for that.