Haven't watched it yet, and also missed a fair bit of season 3. The main reason I watch Glee is for the songs and to be honest most of the plot is to me superfluous fluff at best. Even though I'm gay I'm a bit sick of Kurts "gay" dramas. Also I just never believed the Kurt/Blaine Relationship at all. I actually hoped Kurt would end up with the bully guy who was also gay (who's name I can't remember). Maybe he has and I just haven't watched that episode? To me it seemed almost a foregone conclusion.
But yes I agree with a comment above that the show won't get a fifth season.