According to David Lennon, the answer is more than likely to be yes:
Possible? It's looking about 80 percent certainty right now. RT @Pump_City: is it possible next year mets nontender Maine???
It was only three years ago that the Mets viewed Maine as a stalwart in the front of their rotation for the foreseeable future, but now Maine's future with the Mets is in doubt. Since 2008, Maine's career with the Mets has been plagued by injuries, inconsistent performance, and a declining strikeout rate. There is even talk that when Maine returns to the Mets this season he will become a relief pitcher, which represents just how far Maine has fallen.
Lennon states that the odds Maine will be non-tendered are roughly 80%. There is always the chance that Maine could turn it around this season ans maybe even crack the starting rotation this season, but unless something dramatic happens, then it makes little sense for the Mets to pay Maine somewhere in the $3-$4 million dollar range for 2011.