I am leaning towards, between 35-45 million units LT, Vita will have a rather rough time during the first half of 2013, looking at the 3DS line up.
Feel free to correct me, as I do not have much knowledge on what the Vita will have in store by then, except for Soul Sacrifice.
Check out my Upcoming Wii U Games 2014 Thread
3DS Friend Code: 4553 - 9954 - 4854. Name - David