My guess is that it is going to be Jetfire.
Because he has yet to obtain a figure in the Prime lineup (such as Hot Shot, Sergeant Kup, Ultra Magnus, and Ironhide did), he has ties to Starscream, is a scientist (which would benefit Ratchet), and could help introduce the Aerialbots into this continuity.
That, and it would be a bit of a cliche for them to add yet another Autobot that transforms into a ground vehicle... Especially with the Decepticons having a combination of ground-based and air-based characters.
PrimeStriker wrote:There is no Hot Rod in the Aligned Continuity.
I want to correct you right there - There is no "Hot Rod" in the continuity, but there can be a Rodimus. And with there being more than a single Aligned continuity, they could introduce him as a character that is part of the survivng Wreckers team!