Telltale isn't milking, their games are designed to be episodic by nature with cliffhangers.
I remember when I purchased the season pack for tales of monkey island, they were trying to get ideas together for episode 4, and this was about a month before they release episode 1. Judging from this, I would think they already got at least the first 2-3 episodes already made and in testing, which is why they are solid on dates for those, and not so solid on the finale.
They release on a monthly basis and the entire season (all 5 episodes) cost 25 bucks and it totals a full adventure game that bobby kotick would slap a $60 price tag on if he owned telltale.
I already preordered, I was more pleased with TOMI than the rest of their lineup, Telltale has really made a reputation for themselves.