This may make or break WarhammerOnline.
Mind you there are strong development studios under ownership by major Production studios. Blizzard lives under Vivendi Universal, Bungie under Microsoft (then again I never really cared for Halo). That being said, depending on what sort of arrangements were made, mythic may still have a strong degree of control as to what goes on for WAR. On a positive note, EA will be able to feed mythic a steady flow of green to ensure the project is a success. EA's marketing and distribution machine is the most powerful in the industry, so you wont expect WAR to be some forgotten backstory in the MMO world. When a buyout like this occurs, the previous ownership is ususally pretty good at calling the shots on their turf for the first few years at least. But nobody is really sure what was written in on those contracts.
On the other hand, this game could fall the way of other titles by being forced out into the market prematurely, EA executives with massive hubris could call shots forcing the game turn from bad to worse, etc. Just keep in mind that EA does have some very successful titles out there. The sims being THE bestselling game in the video game world.
It's easy to bash EA, they're the big dog, and are guilty of an endless stream of half baked, poorly produced rushed out the door titles. The poor treatment of their employees isnt any secret, and they are driven by marketing and accounting like any other big studio. Lets hope these negatives dont play too heavily on WAR.
-Grutch