It's a well known fact that X-Men: The Last Stand is considered to be one of the worst comic book movies ever. (right up there with Batman & Robin) There could be several reasons for this, but I think it stems largely from the fact that so many characters either died or lost their powers, so naturally this is going to put a damper on any sequels they make, right? Not necessarily...
The way I see it, there are a few ways that a sequel could be made that might redeem the events of X3.
1: Retcon. One possibility is to take X3 out of continuity and make a new X3. The main problem with this approach is that it tends to confuse people as to which of the movies actually happened. (Movie that took this approach: Superman Returns)
2: Time Travel. This approach basically keeps X3 in the timeline, but someone goes into the past and messes with it so that various events in the series never took place. One problem with this approach is that time travel seems so contrived and it makes it seem like a cheap way out, but let's face it, that movie needs a way out, cheap or not. (Movie that took a similar approach: Star Trek)
3: Reboot. This may seem a little drastic when you consider that the first movie was fairly good, but it might be what the movie series needs. All you'd really have to do is keep the events of Origins canon (or not, depending on how much you want to change things), and just start over from X-Men: The Beginning. The main problem with this approach is that people from the previous version of a series rarely make it to the reboot, and Patrick Stewart is too good of a Professor X to lose, imo. (Some movies that took this approach: Batman Begins, The Incredible Hulk)
4: The Hybrid Approach. You could use time travel to completely erase the events of X3, or use time travel to reboot the series entirely (as opposed to just changing key events).
5: Contrived Explanation of how characters were resurrected or kept their powers. Self-explanatory, but a couple of downsides to this approach is that the 4th movie is going to spend half it's time cleaning up after it's predecessor and the fact that X3 still happened. (no movies that took this approach come to mind at the moment, but it's been done countless times in the comics)
6: Keep making prequel films. :roll:
What do you all think?