With Super Smash Bros, Mario Golf, DKC, Mario & Luigi, Mario Party, Animal Crossing and, specially, the new Pokemon, I think that the 20 million units projection for this year is achievable. But even if it sells one or two million less than that it will be a huge success and it will be a lot more than any other console, home or handheld.
3Ds is already the 2013 winner.
3DS did 14.3m last year (with some major games - not quite as big as this year of course) and 3 months into 2013 it's down 16%+. We're talking about 17.5m in 9 months here, or almost 2m per month. I don't know what kind of boost you guys are expecting from Pokemon, but it certainly won't push 3DS to selling 500k-1m week after week and then 2m per week during the holidays. There would need to be a revision for 3DS to have a chance of reaching 20m.