I wouldn't like an X-Men 4, for a few reasons.
1. Overall, this film wrapped up all the loose ends and brought everything to a close. YES, Magneto moved the chess piece, and YES, Xavier put his mind into the braindead dude, but overall, those aren't large story arcs being left open that need to be closed. X-Men had Wolverine searching for his past: Weapon X. X2 had Jean dying: Phoenix Saga. This just had the cure not working on Magneto (but it obviously worked on Rogue and Mystique; Rogue touching Bobby, and Mystique remaining as Raven when she sold out Magneto... Magneto was just too powerful for the cure), and Xavier being smart. There's no true loose ends. Overall, even though each film has it's own self contained story, they also all play together as one larger story, and a bunch of smaller subplots that remain consistant through each film. So overall, it is one story. And there is a method to storytelling; introduction, rise in action, conflict, and resolution. We have had that with the 3 X-Men films... and when the storytelling process is over, there isn't a story left to tell. Yes, I understand there are story arcs and characters from the comics left unexplored, but those stories aren't the stories of the movies. We'll never be able to have every comic story and character adapted into film. For storytelling purposes, there should be no more films.
2. Look at the complaints we've had already over the deviations taken in this film for Fox to produce a "studio" flick, that they can rush to theatres to beat Superman Returns to prove a point to Singer. Or at least, that's the theory a lot of people around here have.
Do you honestly think, that a movie that doesn't have previous set up (Like the way X2 set up the obvious X-Men 3...), and X-Men 4 will be given the proper conditions to make an adequate comic adaptation that keeps cinematic value, after all the **** we saw in this movie? This movie has Cyclops dying, Rogue being cured, and a very less than accurate to the source material adaptation of the Phoenix Saga. These are all some of the biggest complaints I've heard about this movie (not neccesarily the ones that I share)... do you honestly think that after what Fox did to this film, that Fox is going to all of a sudden change their minds and treat an X-Men 4, which would be an even more obviously made just to cash in on a name than X-Men 3 was, with even more respect than they did with X-Men 3? Absolutley not. Any attempt at a 4th movie would become totally a film by commitee, by the higher-ups of Tom Rothman and his cronies. You guys are already *****ing about the film by commitee approach to this movie, but you somehow think that won't happen for a 4th movie?
So for quality purposes, an X-Men 4 shouldn't happen.
3. And last, but definatley not least... it was hard enough to get the cast back for this 3rd film... and this was a film that was neccesary (there were still many loose ends in the X-Men film universe that needed to by tied up). There would be even more of a chance of losing cast members this time around. Some people say that recasts can happen, it doesn't matter... but I don't want to see recasts. It ruins the continuity.
And I don't want to see characters dropped, either. I know there his a whole ****load of characters in the comics, but it is my belief that you still have to retain a core of the vital characters from the source material, those characters being Wolverine, Storm, Jean Grey, and Cyclops. To me, those are the most vital charcters in the X-Men universe. Yes, there may have been comics without them, but in a more self contained universe, such as the movies, which is an adaptation, you don't leave stuff like that out. I personally don't want to see a movie team of Iceman, Kitty Pryde, Colossus, and the introduction of Gambit. That might be a cool team in the comics, but not in the films.
So for continuity purposes, there shouldn't be an X-Men 4.
I'm glad this film is making tons of money, but part of me wishes it bombed. I don't want Fox to see this movie be a huge success, and think that they can just "summer popcorn flick" the **** out of the X-Men to make a buck every couple years, forsaking vital characters for their desire to give the big stars the leading roles.
This trilogy has already seen the deaths of Cyclops and Xavier (even if he did come back), an inaccurate to it's roots adaptation of the Phoenix Saga, no connections from Wolverine to Sabretooth or Lady Deathstrike, no Gambit, and the curing of Rogue without her ever even getting a glimpse of her comic powers.
These aren't all complaints that I have with the movies, but they are all deviations from the source material. Some more serious than others.
But the fact is, if this franchise continues to go, it's gonna become more and more about the money, and those deviations are only going to become worse, and more frequent, in the studio's quest for quick money. And the X-Men are too important to me to see them become that.
I don't want anymore X-Men films... Wolverine, X-Men 4, or otherwise.
We have 3 great films that, despite some inaccuracies to the source material, in the greater picture, capture the essence of these characters and the world they exist in, and capture the essence of what this story is about, and why I love it so much. I find that to be very fortunate that we've gotten that.
Now let's just enjoy what we have, and remember that sometimes you need to be careful what you wish for... cuz you just might get it...