The thought is that Talib prefers to be released so he can sign with the Patriots, who he has played for before and would help solidify a secondary that figures to be losing Malcolm Butler to free agency. Talib does not have a no-trade clause in his contract and the Broncos were working on a deal to send him to San Francisco, which is when he said he preferred New England.
Talib's contract is also not guaranteed until Sept. 1, so the Patriots could, in theory, get him to sign a new deal on their terms if he really wants to play in New England again.
The Patriots are still rumored to be in on Richard Sherman as well, but with this report, it looks more likely that they will end up with Talib. Of course, things can change in an instant.