From what I understand, the transmission in the 2013 F6B is same one the Goldwing 1800 has had all along. It seems it is pretty rare for folks with the 2013 and older bikes to have problems. But, Honda must have been losing enough money on warranty repairs to make the expense of changing the transmission worthwhile.
Try googling "BMW final drive failure", then google "Goldwing transmission problems". That should make those who have the 2013s feel a little better. I think even considering the small potential for transmission problems, the 2013s are still great bikes. That said, I'm still going to hold out for a '14.