Obviously Nick Mangold is not going anywhere. He is the best center in the NFL and entering his prime. The Jets signed him to a deserved extension in 2010 that will keep him in green and white for a long time. Jets fans have been very lucky to have had top notch center play for a long time starting with the signing of Kevin Mawae in 1998. Mangold took over in 2006 and has continued the incredibly high level of play. Few teams have gotten such consistently high caliber play out of a position like the Jets have from center.
Mangold's 2011 was not his best year. He had a few bad snaps like the killer one against the Giants on the goal line. There were some bouts with penalties like the pair he had against San Diego, one of which wiped out a touchdown. His iron man streak ended as a high ankle sprain forced him to miss the first two starts of his career and hindered him a bit after he returned. Be clear about one thing, though. Mangold at less than his best is still arguably the best interior lineman in the game. He consistently won his battles in both run blocking and pass protection even when faced with top notch competition.
If you need evidence, look at the way the line struggled when he was out of the lineup against the Raiders and especially the Ravens. With Mangold in the lineup, normally the offensive line has an anchor up the middle. The center handling a tackle by himself has an effect that radiates. Guards can turn their attention further outside to assist the tackles. When the center cannot win a one on one, the guards have to help, which means less blockers available outside.
Colin Baxter's play in those games was a monument to Mike Tannenbaum's poor job building depth along the offensive line, but I think the Jets probably would have only fared marginally better with somebody like Robert Turner. Mangold is so good that a dropoff to even an average player is monumental and almost impossible to overcome.
Lucikly he will be back in 2012.