Well, if there had been another season, the characters wouldn't have all moved out of the mansion. Probably more crap episodes about Will hitting on girls, Carlton being stupid, Geoffrey wisecracking to keep his sanity, etc.

Being that Will was the only family member who stayed in Cali, I'm assuming it would have been about him finishing college and maybe continuing his education and eventually getting married and starting a family. I'm also assuming that the others would have made guests appearances every now and then.