Ghost was canceled. It got pushed back a lot, became dated, and Blizzard decided to suspend production in preperation for "Next gen consoles" Now the X-Box 360 is out and no mention of continued development. Blizzard has done this before. Canceling games it doesn't think will meet its quality standards.. ever seen a bad blizzard game?
As for Starcraft 2, if you got the bonus ending for Warcraft 3 they had art for starcraft units was already done. My guess is that they planned to do Starcraft 2 with the Warcraft 3 engine...
Then world of Warcraft came out.. and Blizzard discovered they could print money. WIth the mad profits of WoW Blizzard looks like they've thrown full efforts into expanding that money maker. If they have any other projects going on they're keeping them deeply under wraps.
But I'd be shocked if there wasn't some version of Starcraft 2 in some stage of development.