I recently completed a rewatch (didn't take that long, considering how few episodes there were) and I agree with Third Nacelle, you can always find new jokes. I catch something new everytime I rewatch.
I think part of the problem with season 3 is that they knew they were about to get cancelled, so they had to shoehorn in some type of resolution. I don't think they ever planned on ending the Bluth family's legal troubles. Based purely on the season 3 finale (and the promo pics that were released), I would say that Season 4 is going to focus on Lucille being in jail/house arrest, but you never know.