I think 3 projects sounds reasonable. Isn't Obsidian's goal to have 3 projects(big or small) going on at all times? Or maybe I misunderstood(wich is very likely).
With that said, I can understand your worries(WUE). Too many projects could be a problem, but let us hope for the best. They managed to work on Alpha Protocol, Fallout: New Vegas (and Dungeon Siege III) at the same time. Maybe we are seeing a new Obsidian that can handle several projects.