I think you’re mistaken. Blizzard has so much more going for them than just (World of) Warcraft. Blizzard is developing games for the console market and has still one of the greatest worldwide multiplayer tournaments. Even Discovery covered the Starcraft championship. I think WoW will dominate the MMORPG market for the coming years. Blizzard is going to release the first expansion at the end of the year so most players are going to buy it. I know I will 😉 Blizzard even said that in the future they might even update the graphics. Don’t know how they are going to do that but still… They Warcraft well is like an inexhaustible well.
It’s is true that Blizzard doesn’t develop a lot of games, but they don’t have to. Almost every games they develop is a real gem and sells millions. Just wait and see, if Blizzard announces a new game (Diablo 3), the world is going crazy! Look at Rockstar, they ‘only’ have one franchise and that is GTA. As long as people are interested in GTA, they are going to sell millions of GTA games.
Blizzard is here to stay…