Well when Blizzard first changed their Blizzard.com splash page, I, like many players, wondered if the game they're planning to announce on May 19th had something to do with the first two Warcraft games. But here's practically proof that that isn't the case-- they've updated their page now to Diablo (released in 1996), with a nice quote from Deckard Cain.
So it looks like we're going to get a countdown of Blizzard over the years. The announcement is coming this Saturday, and I count four days in between now and then (and four games left in the countdown), so it seems that by the time we hit WoW, Saturday will be upon us and we'll know what Blizzard is planning to do next. I'm just wondering what cool quote they'll use for WoW-- there's no way they'd do it, but "Mgurrurggugrle" would make me laugh a lot.
At any rate, speculation can shift away again from another Warcraft RTS, and back to Starcraft II or Worlds of Starcraft!