According to this article
by ESPN's Buster Olney, the Twins are expected to make a decision soon, "perhaps as early as Tuesday."
On Monday, Minnesota executives asked for "last and best offers" from other teams involved in the Santana trade talks. The Twins are still seriously considering keeping Santana through spring training "in the hope that a more aggressive market for the left-hander develops." Olney cites conflicting sources about whether Boston is willing to deal Lester or commit to the six-year, $150M extension thought necessary to win Santana's approval. The Mets "have indicated a willingness to offer a package of four or five players." Olney also states that the "Yankees appear to be not presently engaged whatsoever in the Santana talks," but concedes that their stance could change, depending on Andy Pettitte's situation.