There is speculation going around the global fansites that it is fake... but neither side (for or against it's authenticity) have given any proof either way yet. The original posters don't even say where the photo is from, or why it is the only photo out there from this mystery event... and the people against are only using that and the name of the character as reasons for it being a fake.
(the name bit... in Japan, the Gen1 character is actually called "Bumble", so a JP Masterpiece of Gen1 Bumblebee would not be called Bumblebee... just like Sideswipe is Lambor, Optimus is Convoy and Ravage is Jaguar, etc).