It's been done several times in comic books-going back to the Marvel days-and 'sort of' in the original animated series (Some of the characters in season 3 of the original G1 Transformers are supposed to be older GI Joe characters or their offspring). Apart from the Black Eyed Peas referencing Cybertron in their end credits song for Rise of Cobra However, could we be seeing a team-up movie on the horizon? The GI JOE movies haven't been as big a hit as the "Bayformers" movies, and I'm sure critics will hate it as they hate everything Transformers going back to even the animated movie....
This should only be done if it has no connection to the Bayformers. I actually liked both GI Joe movies, they don't need to be infected by the stupidity of Michael Bay. It's an cool idea by itself, but in reality it would just be another Transformers movie with the Joe's replacing the generic army men that are usually in the Bay Transformers movies. Now, a GI Joe/Transformers movies done by the people behind the GI Joe movies could be fun, but I doubt they'd ever do a movie involving Transformers without Bay, so its not something that I think will ever happen.
I don't know what got worse reception, and I haven't seen age of Extinction, but I liked Rise of Cobra a good deal. It wasn't amazing, but I thought it was a solidly entertaining, although flawed, movie.
T4 just got lauded as the best ever Movie in China, in terns of box office receipts. I don't trust anyone involved in the GI Joe movies currently.
Maybe the if even the worst Japanese voice actors in the dubbed Chinese version of Transformers 4 are all still the Anthony Hopkins of Chinese acting? Although, if we translated the Japanese dubbed version of Transformers 4 back into English, it's going to have lot more about how the robots like to violate each other off camera.