It's a battle between MK7 and 3D Land for sure. At the moment, 3D Land is actually outlegging MK7, so it's looking rather definite that it'll be the winner.
3DLand is possibly going to have sold more in 2012 than MK7. That's pretty amazing, really.
It's probably still going to be a while before either of them passes 10 million, though. 3D Land should sell around a million by the end of the year, and MK7 around 900k, putting them at 8.2 and 7.6 million. If they then drop down to the pre-holiday season sales 30-40k a week, they won't actually make it before next holiday season.