Sadly, I don't anything but F2P minigames in Blizzard's future. Overwatch only came up because they most work from Titan.
I mean, why invest millions of money and years for a game (and taking a huge risk) if you can create a dozen skins and sell for the same?
Yes, I'm being salty here, but as long as people buy cosmetic itens for the price of full games, that's what they will get.
Now, @Topic, I would hope they would do much better graphics than HotS for a future MMO.