The game will be finished in December, but from the publishers side all we are hearing that December is bad month for RTS games, and we got to shift release to February. This might change, but imo only in February would DoF be available retail. There might be earlier online release though.
But worry not - all the people who are waiting for release will be playing beta well before DoF hits the shelves.
There is also one more X factor to consider, there is a chance we might get additional funding to GREATLY upgrade all the game art and visuals, if this does happen that would delay release by another 2 months, but doesn`t effect the beta.
Competition is definitely a factor as well - but the main game to watch out is Starcraft 2.