Even if Jackman were to take a paycut, it wouldn't be entirely up to him. The agency that represents him would not allow him to lower his salary more than 50% for a studio picture with what will probably be a $200+ Million budget. Actors like Jackman, superstars, can't sell themselves short - just for the sake of maintaining their superstar image. This is pretty much what happened with Norton on TIH. They got cheap on him and as much as he loved the character, he walked. Its financially irresponsible to allow a studio to undercut you. That's Hollywood. If it were to be an independent feature, then its no biggie, hell - some actors will work for free to do small films.
Marsden is cheap but Berry and Paquin aren't. At least $20 Million between the two of them.
Ellen Page will say no. Romijn, Ashmore, Cudmore and Janssen won't cost alot, but Foster, McKellen and Stewart will cost at least another $30 Million combined.
I would watch it, no doubt, but its just unlikely for the studio to blow that much money on something that might not make it back.