StarCraft HD would provide the same gameplay, but with higher resolution, and improved user interface, making the 1998 original return to the spotlight. Blizzard might be revealing the game in November when BlizzCon is happening.
However, the StarCraft 2 World Championship Series finale will happen in September, and it’s likely that Blizzard will confirm the existence of StarCraft HD here, followed by gameplay and more news in November. Last year’s SC2WCS finale in Krakow, Blizzard revealed the release date and the opening cinematic of Legacy of the Void, so they tend to have announcements during this event.
It looks like we will be able to do some zerg rushing again next year.