I don't think junk heap will actually appear, and besides him, none of those baddies are truly decepticons
Their is potential for him to appear as despite what other commenters will say we don't entirely know all the Decepticons of the film - as I doubt its just Stinger, Junkheap, Galvatron and Lockdown (Especially considering the Autobots have the Dinobots) I believe Junkheap was spotted in the final battle... or at least a Garbage truck shown following the other Decepticons. Bio seems to suggest that they ally themselves with the bad guys and Decepticons - so for the sake of this topic they are effectively the bad guys/Decepticons.
there will certainly be other Decepticons & Autobots in this that they have not shown in the trailers...there always is. Cyclonus was heavily rumored from the beginning although that does not correlate to him actually appearing as we've seen in the past with the likes of Air Raid, Arcee (although she eventually appears in 2), Warpath, etc. I, for one, hope he is in it because one of the worst parts in the trilogy is how Starscream was killed off...I genuinely hate that scene and it's literally the scene before Barricade Returns! and i couldn't even really enjoy it, ya know?
He will but he's not a main Con. He may only be seen for a few seconds to a minute or so and then die.
Woa, so you're telling me the only Decepticon to live throughout TF3 was Junkheap? That's epic. That would mean at least 1 Decepticon survives at the end of each film.