I too share your concerns about the development time. I don't think it's enough, even though they did produce Heretic 2 in record time and that was a good game.
Judging by the new vid, they have worked quite fast in getting up to speed with the tech for the game, and while that probably needs some tweaking, I don't think it's going to change radically before release.
That probably means the bulk of the time will be going into the level creation, weapons, scripted events and cut scenes, and enemy AI.
We already know that you will not be able to choose Light or Dark side - and to me that is a fundamental part of JK that is being omitted in the sequel. Without the moral play, I don't think it will feel like the same type of game. If nothing else, I think the development time should be extended slightly to put this feature back in.
I think the levels are going to need a lot of work...if they are aiming for the size and complexity of those in JK. And the secrets in JK were mostly well thought out, often making you stop and think about how to reach them. Will Raven have time to implement such features effectively?
I take the view that we've waited this long for a sequel, so it wouldn't really bother me if they aimed for the end of next year for a release date.
However, lurking in the back of my mind is a nagging little voice...which says by Spring 2002 the Q3 engine is going to be showing it's age, and although it will be helped immensely by Raven's modifications, it is not going to improve with age.
I imagine that Raven will be wanting to get their hands on the new DOOM tech as soon as possible, to tweak the hell out of that, and use it for their next set of projects.
Speaking of which...is there any chance of a Heretic III?