Hummm..... A new Prime you say?
Well, going off some of the ideas that have made it into past comics, but never made it into toy form, I would really love to see a toy made of the Optimus Prime Hiss tank from the G.I. Joe crossover by Devil's Due. I think that think looked sweet! And as someone else mentioned, the 1930's era Optimus Prime from the same company looked pretty cool, so I think a toy of that Prime would rock as well.
Also, as previously mentioned, the World War I designed used in Dreamwave's Joe crossover was really sweet, and is another design that really deserves a toy. Here's a couple scans from the comic for a visual:
Along those lines, this Prime never made it into any comics, but it's a pretty sweet design based off the G.I. Joe Rolling Thunder vehicle, and I think it would make a good Optimus Prime:
Another interesting take would be Optimus Prime with a beast mode. And no, I don't mean Optimus
Pimal, I mean Optimus
Prime. Something besides a monkey, or a mammoth, or a white lion. Maybe something like the dino-mode Optimus hinted at in the beginning of Hearts of Steel (I think one of the writers or artists once said it was a brachiosaurus?).
The idea of Optimus with some kind of jet mode that was posted a ways back sounds interesting. Done properly, I think that could probably look really cool, so I'd be open to seeing something like that.
I think what's more likely though, is that the next
TF series is going to be some kind of animated take on the live-action movie-verse. Now I'll probably get stoned by the masses for saying this, but I think if they took the movie-verse designs, cleaned them up a bit, removed all of the extreme, minute details, and made them look a little more like the
TF:Animated designs, well, I think that would look pretty sweet. In my minds eye, the designs would look more smoothed down and slick, like the Animated designs, while still retaining some of the movie design cues. I know this probably seems like a contradiction of terms to many people, but I think it would work pretty well. Anyway, just my two cents.