Honestly, I'm not that surprised. The Jets have been very carefully bringing along Jeff Cumberland from his first year with the team in 2010. As best I can recall, the Jets never exposed Cumberland to the waiver wire since joining the team, but the Jets did place him on the injured reserve after he tore his Achilles tendon against the Raiders in 2011.
Cumberland is a far from perfect replacement for Dustin Keller, but he's still learning the nuances of playing TE at the NFL level and seems poised for more production based on some of his 2012 numbers. Remember that he was at the mercy of Mark Sanchez much of the season when he was working in replacement of Keller, and I can't even begin to remember the number of times Cumberland had to reach backwards to try to catch passes thrown behind him. Truth be told, Cumberland was a bad run blocker in 2012, but did much better as a pass blocker / protector during the 2012 season. Funnily enough, Matt Miller tweeted me early Monday about Cumberland how he liked what he saw, and while there was room for improvement, he might be poised for more growth in 2013.