The issue is trying to maximize sales of the Wii version IMO. I think ideally they want to max out the Wii sales, and then unveil the Wii U version.
I think it will be early 2013.
If it was a normal retail game, you would be absolutely correct.
However, since it's fee based MMO, most of the revenue they expect will come from the subscription fees anyway. Now selling people the Wii version first, may backfire; that is, people will buy it and then continue to play it until the Wii population runs out of the steam. Now, they have to buy the same game this time on Wii U by spending a capital money; there's a good chance they spend their money somewhere else or at least delay their purchase.
Personally I would be very impressed if DQX passes 1 million in Japan considering it's a MMORPG.
if it passes 1m, it can become one of SE's most commercial success...
I mean, even if they play only for 1y on average, how much will that bring to SE? I think the revenue would be around 300m dollar, around 5m retail game sold at full price, and probably their share of the monthly fee is much more than the retail share.