Well, look. Horii has said several times that he a) has heard fans saying they want another game like DQ8, and b) would like to play the next game on big screens. But I don't think this particular announcement means anything, either way. I would expect the game to be multiplatform in some way, though, based on past comments from Yuu Miyake.
What I think it boils down to is this.
The PS4 had an absolutely disastrous start in Japan. All excuses aside, if I was a shareholder in Sony I would have been extremely worried. Will it pick up after this showing? Absolutely.
But DQ11 has already been in development for a while. And Horii has always been adamant that he puts DQ games on the most popular console of the era, to maximize the number of potential players.
Could the PS4's horrific launch have "disqualified" it for DQ11 early on in it's development, and thus left it defaulting to the WiiU (or 3DS)? That's the thousand GP question at this point. As such, we just don't know how long DQ11 has been in development to really make any judgement calls. I would be surprised if it was PS3, for example.
(Although the rash of PS3/PS4 games, including DQH, surprised me. It goes to show just how scared the developers in Japan are of the PS4 not pulling out of this mess.)