[opinion]
If I had the option to tell Blizzard exactly what to make, and trust them to do it right, I'd want a StarCraft 2 worthy of the name. By worthy, I mean:
1) Heroes are NOT the center of the game - WC3 was essentially a party-based RPG with summoned monsters. Which I didn't appreciate.
2) Gameplay mechanics that revolutionize the genre - even if you didn't like SC, it WAS pretty much the first RTS with unique sides (contrast Age of Empires, Star Wars: Galactic Battlegrounds, SW: Empire at War, and WarCraft 2). Mix it up, take a chance, make the leap!
3) NOT MMO. Thanks, but if Blizzard's making it, you can be sure they're gonna charge for it, and I'd rather have $15 worth of Dr Pepper than a month's worth of playing a game I already bought. Give us (free) online options, sure, but don't FORCE us to play online.
Of course, as my pseudo-HTML shows, this is all my opinion.
[/opinion]