Yoshida has been considering dropping to lw even before the fight against Guymon. Though he certainly has a chance against Hornbuckle, I think him dropping to 155 is the path of least resistance. He has already battled some of the top ww's and lost. I know he wants back in the UFC, so if he dropped in weight and looked impressive I think that would be his best chance.
You know I really wanted to see him rematch Dan Hardy as well, I think they should have done that fight before he faced Koscheck.