As PatsFan09 says below, we can say this with the benefit of hindsight now, he really was never coming back. The signs were there during the season, he had threatened to walk in TC and as Mike Giardi said yesterday, he did play in a bit of a mood last season. He wasn't happy, even when we were winning and the defense looked outstanding, he was unsmiling and down.
He was never coming back and as pointed out, BB certainly did not have the money to meet his demands. The only way it could have worked was getting rid of the McCourtys, Slater, Thuney while also allowing KVN and Collins to walk. It would be insane for BB to even agree to a $20M contract for a 43 yo QB on a decline.
This is best for all concerned. Tom will get a chance to prove himself elsewhere with good weapons and a different environment, the Bucs season ticket sales are already going through the roof, the TV figures for NFCS games will be huge and the Patriots have not had to compromise in shelling out for a big contract and not being able to get more firepower. And both men will be relieved when the dust settles.
And when Tom decides to go, he'll return to NE for a ceremonial resigning and a heroes farewell.