Just from reading this thread and what Mr Mearls said about short adventures my understanding is this: The core release will focus on short episodic adventures. Stringing these together will be fairly simple for an experienced DM right off the bat. They will extend this with support modules for more epic scope adventures and options for PC lairs/castles/followers etc.
As for the disappointment that there is no date announced for the open play test to begin, I'd be surprised if anything else were the case. Who really wants them to rush this? Why would you want them to chuck any old slop at us and say: test that. That would guarantee failure. They want to come up with something they are happy with and that they believe meets their goals. When it's ready they will open up the public playtest. We'll bash it to bits and with any luck at the end of it, we'll have a pretty cool game. Meanwhile, there are still plenty of cool games to play.