Sam Witwicky never appeared in the films after Dark of the Moon, leading some to suggest that he died in between the events of DotM and AoE. So let's just go over the facts to see whether he really is dead or not. We know that Cemetery Wind had no rules, no boundaries, didn't flinch torture, human trafficking and genocide, and that they traded dead Autobots and Decepticons for money. They had no problem with attempting to kill Cade and his daughter, and attempted to kill Joshua because he didn't agree with what they were doing. So we can assume they would have no problem ordering a hit on Sam. He was the biggest supporter of the Autobot cause and was essentially a micro celebrity post DotM. He was finally considered a hero for participating in battle and killed Dylan, allowing for the pillars to be destroyed. Because of Sam the military was now aware that the Autobots were back and that they needed to destroy the pillars to end the battle. After NEST was shut down, we can assume Bumblebee stayed with Sam and Carly for a few years, before Optimus sent his message warning the Autobots to cease all contact with humans after the battle in Mexico City, and meet up somewhere safe. Bumblebee would then have to leave Sam and Carly and meet up with the other Autobots. We can assume that Sam probably had government support, since his encounter with Dylan at his penthouse would probably have Sam think he would need security so none of his family were hurt, and so would have security cameras/officers guard his home. He was also considered a war hero, so he would have support from his former NEST colleagues, such as Lennox and Epps. If Cemetery Wind were to have a hit on Sam, it would have to be after Bumblebee left, because the anti Autobot campaign would've been in full effect around this time. If Sam wasn't in protection of the government anymore, he would've likely been turned in for "treason against humanity." Unless Cemetery Wind was able to pull a MLK on Sam, it's unknown what happened to him. What's weird is that Optimus or Bumblebee never mention Sam. If they knew Sam died, they would've been mentioning him to Cade.