He was the only villain to not lose his head unlike all the other villains in DOTM aside from at least one of the Dreads. His body is still intact aside from major damage to his body due to Megatron's ambush attack and Optimus shooting him twice with Megatron's shotgun. However as I said before, "He was the only major villain who DID NOT lose his head" and surely there must be some Energon deposits hidden on Earth somewhere. There are also still many Decepticons left all over the world as the destruction of the control pillar and the space bridge only sucked in the Cybertronian fighters and the Cybertronian warships. So it is possible that a group of Decepticons happen to locate an Energon mine, find Sentinel's dead body and use the Energon to bring Sentinel's Spark back to life. Sentinel would only require a new vehicle mode since his original form as a Rosenbauer fire engine would look all f**ked up due to the intense damage he sustained in the final battle in DOTM.