The competitive types will treat it the same way as CS:Source versus CS 1.6-with a slow adoption rate and much whining and complaining because they have to learn something new after years of playing the same game. It will still be huge saleswise, but I would bet years from now people will still be playing the original game in its butt-ugly resolution.
IMO Blizzard should sort of release a "classic" version of Starcraft (with updated visuals/UI) alongside of Starcraft 2 to spur adoption of the game in the competitive groups. Even then, though, people will bitch because selecting more than 12 units at a time is for n00bz kekeke ^_^.
Competitive RTS gamers HATE change while clamoring for it. I can't wait to see the ocean of tears in the Supreme Commander forums from the competitive players who have complained for a balancing patch, and, having received it, will now complain that the game is dumbed down for the newbies because the build orders and map strategies they have learned after playing 200+ ranked games allow people of lesser experience to better compete with them.
Starcraft HD is sort of a unfair assessment of the game's visuals, though. The animation and lighting/shadowing in particular are pretty to look at. In terms of gameplay I'll give them a pass on their unwillingness to innovate-there's been plenty of innovation in the genre over the last couple of years, and a game that consolidates some of the best points while keeping a classic and familiar game style is fine with me.
The one thing I hate? The interface and camera. Christ, I hope that thing can be sodomized with LUA into something that's not monstrously huge. Between the zooming of Supreme Commander as a intuitive/accurate management/navigation scheme and Big Huge Games' interfaces for PERFECT ease of unit management/micro, going to something that's both zoomed in to the max and taking up that amount of real estate is very, very painful.