Hard question for me. Aside from Titanfall, Xbox One hasn't anything cool announced. We would need to wait until E3 to see a bunch of games that will be released during Holidays. So with the Titanfall push, Xbox One should make 5-5.5M until May. More I don't think. Then we got E3 and we should wait until holidays. After December, the Xbox One should have sold 9-9.5M units, not more, not enough to reach the 10M's roof.
The Wii U gets Mario Kart 8 on May, and it will definitely help sales, 7M maximum until August. Then we got a bunch of games more, like Bayonetta 2, Smash, Hyrule Warriors and I guess Yoshi Yarn, for the announced games, not counting the games that Nintendo will announce on E3. By the end of the year, I think Nintendo's console will make 8-8.5M units, again, not more.
Having said this, Xbox One will make 10M first, not by the end of this year, but it should.
My bet with The_Liquid_Laser: I think the Switch won't surpass the PS2 as the best selling system of all time. If it does, I'll play a game of a list that The_Liquid_Laser will provide, I will have to play it for 50 hours or complete it, whatever comes first.
