Well considering Heroes of Newerth won't be free (it's gonna cost $30 or so according to S2) I doubt it'll get huge like DotA. Then again, maybe it will.
League of Legends on the other hand, made by one of the main DotA guys originally, will be free and I see more people going to that one. But then again, HoN is way more polished and LoL (lol?) needs plenty of polish work.