Also, the show's future depends, first and foremost, on May and Hammond agreeing to carry on. That could mean one of two things - on the BBC with a new lead host, OR, on another network with Clarkson. I suppose a third alternative could be on a new network with a new host, but if they get a new host, I don't see why they'd leave the Beeb.
Honestly, I bet there have already been networks talking today about scooping up the three of them and starting TG on another channel. TG is such a moneymaking dynamo, other networks would be crazy not to consider picking it up.