Let's keep in mind why seasons 1 and 2 were done the way they were. Telltale was a young company and had not yet proven itself. With no track record, people are more likely to bite if you sell a single self-contained episode than a whole over-arching series. The episodes were even made so you could join a series in the middle without losing too much (moreso in season 1 than 2, but you could get away with it in 2 if you didn't mind missing a few references). And Telltale's story writers learned as they went what worked and what didn't, making it possible to improve the story mid-season.
Now, Telltale has several full seasons of quite a few games to show for itself, and individual episodes are no longer sold. That means they can be more interconnected, and they've gone even further with TWD by making decisions in one episode affect the storyline in another. You can't do that with individual episodes. (OK, so they had the car upgrades in S&M Season 2, but that didn't really affect the storyline much.)
So I think if we do get a Season 4, it's going to be a real full season, and it'll work out great. Hopefully more puzzles than their more recent games, though.