It's hard to say without knowing any of the planned releases for the second half of the year and half the releases for the first half. So far the first half looks to be shaping up better than this year's Jan-Jun, but without a huge Western hit like NSMB2 in the second half there isn't much potential for growth. 3DS needs a Pokémon game this year. Failing that, something else big, though I can't imagine what that would be. Even if I thought there could be a Metroid/F-Zero/Star Fox game coming to 3DS next Holiday, I'm not sure that's 'big enough.' The only other franchise I imagine could have a strong effect would be Zelda, and I doubt they'll have one of those ready for 2013.
What else is there? Super Mario 3D Land 2? 3DS needs Pokémon, it needs it bad, and it needs it next year. Even Mystery Dungeon could at least sell a few million and be a pretty big release late in the year.
So my guess is: without Pokémon, 15-17 mil. With a major Pokémon game released in November, 17-19 mil. With a major Pokémon game released in September, over 20 mil.
