Not trying to take anything away from Stardock here, but there are, in my opinion, ways to avoid stereotypes in fantasy games besides chopping out the stereotypical parts (in this case the standard fantasy races) entirely. Why not include unconventional interpretations of classical fantasy races, or create entirely new races? I mean Medieval/ancient humans have got to be the most stereotypical race in fantasy, almost every fantasy has them, even those that do not have elves, dwarves, undead and the like. Besides I deal with humans all day, every day, if I wanted to play a game that only has humans I'd pick up a historical RTS, I want something fantastic in my fantasy games. Something besides flashy magic and unfamiliar geographical features (which are also very common, stereotypical if you please). In any case to conclude with my main point if stereotypical fantasy races are boring, humans have to be the most boring and overused of all.
Now, don't get me wrong, the game still looks awesome and I certainly will be preordering it. The "humans only" thing strikes me as an odd design choice though, especially considering the inspirations for the game. It would be a little like making Total Annihilation 2 without robots, no? In any case I very much hope that Stardock changes its policy and includes "canon" races besides humans, even if they aren't elves, dwarves and so forth and even if they come in expansions.