He hasn't- Sauerland brokers a fight by fight deal with Sky. If his fight was headlining a UK card then it would certainly be on Sky. As it's a Mayweather headlined card it probably will end up on Boxnation.
War ren has already said that Boxnation aren't going to push the boat out for Mayweather vs Berto. Then when you see that Groves is on the undercard, and that ALL his domestic rivals fight exclusively on Sky, it's safe to say that this bill be televised by them. Looking forward to Groves vs Jack far more than the main event to be honest.
Sauerland also made comments about how difficult it was to work with sky (i think it was after the Rebrasse fight) I wonder if that will have any bearing. Then again as far as promotors go it will all be about the money
Sky have a card on the same day in birmingham so they might put the ggg fight on after but boxnation do tend to get the yank fights
Sky have picked up a lot of the GGG fights recently, at the exception of the Murray and Munroe fights I believe. Think they will get this one as it is a fight with genuine interest in it.