Well i don't see why they can't release them the same year. Lets not forget one thing. DQ is not that popular outside of Japan.. I felt sorry for DQVIII's support outside of Japan. Hell DQVIII sold more in Others than it did in the Americas. Zelda however is very big outside of Japan. So they're not going to really affect each other's sales.
I'm actually surprise to see so many people excited about DQX on the wii. Past sales would show that you people don't care too much for it unless you're japanese.
Also here's one thing you should also consider. Zelda is usually a simultaneous global release. DQX is a Japanese release, than many months later released for other nations. Zelda+DQX(JPN) can be 2010, and DQX Others+NA can be 2011!
Also, have you pooped ur pants lately? lol i just had to say it...
