They really haven't announced anything yet (or at least, I don't know anything else other than the fact that they're releasing it), but yes, it's made by Blizzard (the original DotA is owned by Valve, as you probably know). The description says that it has characters from Blizzard's game universes, so it'll probably be something like Smash Bros.
http://eu.battle.net/sc2/en/blog/841898#blog
Re: Starcraft 2
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