I wouldn`t want the next movie (if it happens) to be the prequel of IWTB because that would mean that William dies or something like that
We don`t get Skinner`s current position in the movie, right? Maybe he did became higher ranked in FBI hierarchy and managed to prove that the trial was false (which was) and that Mulder didn`t kill Rohrer and maybe he managed to oull out a deal for Mulder. Or something. like that. Sigh.
And about the qouestion how is anybody able to live normal (or even want to) with the knowledge that invasion will happen in 4 years... Well, what should they do? Sit down and cry over their sad destiny? I mean, one of them must have job or they won`t have money to live with. And who nows what is in all those file boxes in Mulder`s home office. Maybe he did try to find a way to fight invasion throughout all 6 years.