Wii U will reach 10m first sadly. PS Vita is on a downward spiral. Not only Japanese sales can help it and Wii U seems more well rounded now.

Wii U.

We'll have to wait til next NPD numbers for Black Friday month, as well as shipment numbers from Nintendo and Sony to see how both are really doing this holiday season. Having said that, I still feel that the Vita will pull it off, first. It has a 2.2M headstart, something that will take the Wii U a long time to make up. I also think the Vita will see a decent boost in Japan following the PS4 launch, as it complements the system well. It should also see a slight boost WW for the same reason.

As for the Wii U, I don't see it doing too well after the holidays. It may sell slightly more than the Vita, but definitely not enough to make up that 2.2M gap.