Hasbro posted a Q and A on their website a few days ago and among many exciting updates for the entire Star Wars line, this little tidbit of Mighty Muggs information was released:
"Q. Will Mighty Muggs get more accessories/playsets/vehicles/anything? Maybe an accessory pack sold separately, or sold online?
A. Nope - Mighty Muggs will continue to stay as is - a line focused on the unique, Hasbro-created Mighty Muggs silhouette, with small accessories unique to each character, and not as a vehicle/play system. "
So there you go, straight from the Horses mouth. Check out the article in it's entirety here
