After Optimus kicked him out of Cybertron to space, we didn't get to see or mention of Megatron's fate after that. All we know is that Optimus cut his arm off and kicked him to space. Did he crash landed on Earth or is he floating in space? Once again Megatron being weak and useless. We could've had a great battle between Optimus and Megatron, but nope let's focus more on the humans. I wish they can redeem Megatron, but probably won't happen.
It won't matter. He'll be back in the next one with a brand new body and no explanation about what he was up to.
Most likely, the next film we'll find out that before the Fallen, before Sentinel, and before he considered going after the seed...he was working with Quintessa all along, because Megatron just is always working for someone else!
Nobody's bitch he says... Note they are all Primes? My old theory is that Megatron kept Sentinel close so he can take over the Decepticons backstabbing the Fallen and stopping the war as the Autobots follow Sentinel Prime. As a Prime can kill a Prime or so is believed. Megatron knows a lot of stuff I'd believe he started out as an archivist.
If they didn't explicitly show him dying he's not dead. These movies really like to shove it in your face when a character dies in the most gory way possible.
Interesting that Megs was thrown through a wall and out into the open air...very similar to Rodimus throwing Galvatron through the side of Unicron, and him falling away to who-knows-where.
He can turn into a jet so I'm sure he's fine, as long as that 1 arm didn't form anything crucial. I hope he keeps this body for TF6.