I've struggled with how this one is going to add capacity. It is another Ka Low sat. There is more room in Ka High, but it is my understanding that Ka low is maxed out.
Because of this, I've come to a theory: D12 is more of an in orbit backup than anything. Not to day it's going to sit idle. But I think DirecTV is too nervous about something blowing up on D10 or D11, and having all those HD subs run to dish in the year it would take to get an on ground spare into space. Heck, maybe they had an extra launch slot due to the cancellation of D13, and figured they would launch a sat rather then lose some kind of deposit. Also, I find it odd that DirecTV would go to the expense ordering a sat to backup 2 satellites, yet they haven't ordered a "D14" sat to be a backup to 3 satellites.
Even the DBStalk gurus couldn't really explain to me how DirecTV12 could expand capacity, other than a bunch of platitudes about DirecTV being smarter than us, and maybe they can shuffle around some spots and free up some TPs.
Maybe like the poster above said they figured out a way to swap out the Ka Low for a Ka High payload.
But what do I know, I'm a Dish sub.