The Mets kept Reyes on what likely are to be two false premises: They were contenders, and they had a chance to retain the shortstop in free agency.
Indeed part of the reasoning behind not trading Reyes was that it would likely make it easier to re-sign him this offseason, but it's revisionist history to suggest that the Mets thought they were legitimate contenders at the time. They had already traded Carlos Beltran, for one thing. Moreover, the Mets held onto Reyes because he had become considerably devalued by his recent stint on the disabled list (and obvious lack of full health subsequent to that stint), and because they would have been pilloried (and punished monetarily) by the fan base for trading their (the fans') favorite player.
It's also dishonest to baldly assert retroactively that a premise was false, as Sherman does here. Whether or not the Mets have now decided to punt on 2012 and, in so doing, make a clean break from the Reyes-Wright era, it doesn't necessarily follow that they held that same position when they elected not to trade Reyes last July, and a change in that position in no way falsifies what was a perfectly defensible premise at the time (i.e., that keeping Reyes would improve the Mets' chances of re-signing him this offseason).
It's par for the course for Sherman, though, who doubtless has at least a half-dozen "Mets are fools for letting Reyes leave" columns in the bag to cover that eventuality, with a commensurate pile of "Mets are fools for signing Reyes to that contract" articles to address the other outcome. It's win-win!