For a while, people were running old World of Warcraft servers that were not official and were pre-expansion packs. Blizzard had them shut down, of course, but today at BlizzCon, they surprised everyone with this announcement.
War of Warcraft Classic is coming and they will be vanilla servers for folks to play on. That's quite a big undertaking as running two "versions" of the game can be quite daunting. They seem to have figured something out though, so for those who want to play the original World of Warcraft MMORPG, your wish is coming true.
No word on when they plan on making the classic server available, but it's great to see Blizzard listen to fans and bring them something they really want.