Soundwave, Hot Rod, Seekers and Galvy seem the most obvious.

 

i don't know if they will do the other seekers for a while - out of the 8 MPs (the non sequentially numbered ones don't exist!) over a third of them are seekers already.

then again, there is the compulsive Pokéseekers factor. and the extra articulation means the long-awaited conga line of seekers will finally be possible.

hotrod is highly likely, ultramagnus less so (he'd be three foot tall ffs!). i wouldn't be suprised to see Jazz either.