I'd guess that Belichick probably wants to see how Brady performs over the rest of the season before he commits to anything, which--provided that doing so doesn't offend Brady to the point that it incites him to leave--is a smart, if cold, move on his part. AKA exactly the sort of move I'd expect Belichick to make. He knows we're in uncharted territory age-wise.
I really, really hope they come to an agreement and Brady retires here, but nothing would really surprise me as an outcome, and no outcome will make me like and respect either one of them any less.