My next 4 pieces will be:

#00 Optimus Prime
#07 Sideswipe
#09 Starscream
#12 Minibots

That will take some time to find, since I have no leads on 3 of the 4 items.

I still have Alternators on the horizon, so the hunt for Decepticharge and Prowl is never ending.

And there's a few Cybertron pieces I'm looking forward to, Evac (Live Convoy) and Ligerjack (Leobreaker).