What if you don't sell out Lambeau??? As a falcons fan I can assure you blackouts suck. Imagine the Green Bay Area not being able to watch the Pack, in a playoff game on TV. I'm sure it will never happen but it's fun to think about.
You're right, never happen, if they aren't all sold, the GB Packers organization then purchases the remainder of the tickets.
Don't forget it is not just the Green Bay area. The Milwaukee area is also considered home market which is outside of the 75 mile radius applied to other teams. That said, one way or the other it will be on TV. 40,000 tickets to be sold in a few days for a late Sunday afternoon when nobody thinks they will win is a tough sell even to Packer fans. There are only 7,500 remaining as of this morning.
Green Bay Added 3,000 seats from last year, and didn't even know they were going to host a playoff game till Sunday night. 40,000 sold in 4 days? Thats pretty incredible when the temps might be -20. Im impressed, non-story IMO.
Plus add in the fact that they have sold out every home game since around 1960. Most people didn't even know there were tickets available because we are not used to being able to buy them the regular way.