there are plenty of ways they could make another x-men after x3...BUT there are some glaring failures about that film because of how first class sets things up. there are so many things that i feel first class and its inevitable sequels will contradict that both x3 and wolverine tried doing something different with. i own both and have enjoyed them but it seems like this new approach with first class and its characters which we will be getting more time with in will just fuel the writers to take liberties where they feel are necessary for their stories in regards to where x1 and x2 went with the characters. i have a strong feeling that if first class is going to retcon things that were done in anything made after x2 its very possible we might end up getting different takes on where sabretooth came from and how he was recruited to the brotherhood and possibly his relation to wolverine before we see his character, maybe a different take on stryker that would involve his son, and i could even see them bringing in juggernaut as a non-mutant and a relative to xavier like the comics.
im not one of those people that will bash x3 because of brett ratner, the only things i hold against him for that film is cutting scenes that should never have been cut (juggernaut getting wolverines blades through his arm, the extended phoenix destruction at the end, having rogue get rid of her powers, not showing the first reveal of magnetos lair and a few others). i think the people that wrote this film should have looked to bryan singer and what his vision was going to be for that film and adapt it with him possibly producing seeing as he pretty much started the franchise. an x4 would probably be a good thing to try and do, i just think the only reason to remake x3 would be to make a better film. hell, if they could reincorporate scenes from the last stand id be all for it.
the things i think that were unwise to do in movies made after x2 were to try to show xavier walking but bald and friends with magneto because thats such a big deal and yet they were just throwing it in there just to try and say 'hey look this is kinda cool' and the same thing goes for wolverine. i can overlook emma frost being in that film cuz shes not really anything more than a one-shot cameo and i could pretend its a different character. same thing with deadpool, i dont mind that take on the character. the thing that bothers me a little is the difference in wolverines origins then the way it was portrayed in x2. those flashbacks should have been reshot shot for shot to match up with the sequel. in that film stryker even was depicted as having glasses yet he doesnt in the origins film. and sabretooths look should have been more reminiscent of his look in x1. his claws, eyes, hair...it should have matched even just a little.
if an x4 is made, its not like you can just ignore x3 because magneto and rogue are both powerless, xavier, jean and cyclops are all dead and it just would be a hard film to ignore if they continue on. it would have to continue on and try to be more creative then its predecesor but i just think an effort shoudl at least be attempted for a talented director with the way bryan singer would have ended the trilogy to be pitched to the actors from the first 2 and see if they would be willing to come back. im not going to expect it to happen but its not like singer hasnt done something similar to that in the past. companies are used to rebooting the characters and franchises so it wouldnt be a far shot to try, but i dont think there has ever been a film that has had an installment remade with the same actors that cuts out a previous version. itd be neat so see it done and would give a future x4 or beyond more to work with. i dont think the studio would kill xavier or cyclops and i think cyclops would become more important instead of it revolving around wolverine. wolverines cool and all but she loves scott.