Things I feel I need to consider:
-Does it produce the type of game I want?
-If not, can it produce the type of game I want with add ons?
-Assuming it can produce the type of game I want with add ons, will those add-ons be available? (Currently, the things I've read seem to suggest that the particular add-ons I'd want will not even be looked at to start work on them until quite a while after the system is released.)
-How many add-ons will I need to be able to play the type of game I want, and do I feel more like I'm buying add-ons because I need to or do I feel more like I'm buying them because I want to?
As it stands, the answers I seem to have for those questions are (in order): I don't think so; possibly; not for a long time, and I have no idea.
It seems likely that I will play the game. I have enough friends who play D&D that I imagine at least one of them will buy something. It seems unlikely at this point in time that I will purchase the game. A lot could change (and I expect it will) between now and then, but my current vote is that I do not plan to purchase the game.