Just some speculation on my part.
Yuji Horii says the game is in development for the big screen not mobile/handheld.
SE releases DQ Heroes on PS3/PS4, thus at least to a degree signaling to DQ fans "this is where DQ is going", remember the Wii got some spin off DQ games as well before eventually getting DQ X.
I recently read that SE thinks that FFXV is crucial to the success of home consoles in Japan and that if it fails there might not be much of a home console future over there. Read here. This sounds like a certain disregard of the Wii U already.
I cannot think of a single SE game in development right now that is coming to Wii U. Now granted the Wii didn't get a ton of SE games either, but it got a couple at least. The Wii U only has the DQ X port for now, if I'm not mistaken.
So while non of this is proof of course, I still think that we can book DQ XI on PS4, possibly even exclusively, as a very real possibility for now.
