I'd like to believe that right now, but I'll wait until that actually makes business sense.
Bethesda has id games to publish and FO3, they can sit on ES for 2-3 years. Zenimax on the otherhand has "TES:O" and that is on deck and about to be Zenimax's turn at bat. Then 2012/13 rolls around and TES:V goes on the next-gen consoles as well as PC. See how that all fits so nicely?
No, they don't, Bethesda
Softworks has id games to publish. Bethesda Game Studios is done with Fallout 3. They're making their next game right now. Zenimax Online is making an MMO. The MMO can come out in, say, 2010, and then TESV can come out in 2011. Even taking the MMO out of the picture, TESV will come out in 2011, because it's only been in development since October 2008, and Bethesda games take 3-4 years to make. The MMO and TESV will not interfere with each other if they come out a year apart, because one game is an MMO, and the other is a single player RPG, and those attract different gamers. Saying they will "compete" with each other is like saying Fallout 3 is competing with Oblivion. The profits of both games are going to the same exact company, so they are not competing, and neither will the MMO and TESV.