I gotta wonder how long maps will be free. The resources they're spending on maps could be put towards more heroes or skins which will get them more money. But new maps, while keeping the game interesting, don't directly put any food on the table so to speak. Maybe they'll open map making up like SC2 once the game releases.
That said, have they said which heroes are under development? Sylvanas is next of course, but then who? I've heard rumors of Kael'thas, Dahaka, and D3 Wiz, but that's about it. Oh, and ppl begging for D2 Necro.