I've heard it both ways as well.
The ideal situation, for me, was to have a two-part finale (ideally written by Sorkin, as was rumoured back then). Part one is Vinick winning and our characters coming to terms. Where Vinick is obviously a really good guy and will do the right thing, but nobody thinks he can truly change the Republican Party (as our characters see it).
Part two is having Rob Lowe come back as he did, perhaps as a California State Senator who just won the California Governor's race—even better if he's married to one of his previous relationships we've seen—and him and Josh re-enacting the Leo/President scene flashback scene "Bartlett for President" napkin.
Oh, of course, the Josh/Donna relationship as well with Sorkin's excellent banter

.
Also wished that Sorkin would've stayed on for the entire run, or at least was still involved with the show, but wrote say 10 or 11 episodes per season, starting from Season 5 on. Wonder what would've been different? Perhaps I'll ask him one day.
As much as I absolutely love Sorkin (one friend of mine said I spoke like a character on the West Wing, that was the best compliment of my life) 9/11 + Bush really screwed up a lot of Season 3-4 West Wing.
Furthermore he made the critical error of not focusing Season 4 of the West Wing on a proper Republican/Democrat showdown election campaign. He was too angry at Bush for winning. And there's smaller stuff he could have handled better.
The only three things that post-Sorkin West Wing did right were the Speaker of the House (charming smart obviously Newt Gingrich fellow), the Supreme Court episode, and the idea of devoting a huge chunk of time to the campaign in the last couple years.
A Season 4 West Wing with a McCain analogue instead of a Bush analogue as the Republican nominee with Sorkin truly giving the Republicans a fantastic nominee and having Bartlett win anyway would have been lovely.
ETA: I know I'm a terrible person (kidding, incidentially, since the Intertubes suck at sarcasm) but I read a lot of West Wing fanfic back in the day (I couldn't handle post-Sorkin West Wing) and there is some really nice stuff out there.
ETA2: Sorkin got his ass fired because the expense of turning in scripts late + Sorkin being on cocaine all the time was a hassle. There's no way he would come back for x amount of episodes for season 5, and honestly I don't think he'd be up considering Studio 60.
Given Studio 60 versus the Social Network I'll wager he just needed time to learn how to write again without the cocaine which means a Season 5 with lots of Sorkin probably wouldn't have been that good. On a happier note, I've read the script for his new HBO show behind the scenes of a political news show and it is fantastic with an absolutely brilliant twist.