First off, Serra will never drop to LW. He has said so repeatidly he loves his pasta way to much.
Second, if he were to lose, WW is so stacked there are still a ton of guys for him to face. I would guarentee he fights Hughes next if he loses, I think he wins that fight . Which with one more win could setup another title shot.
EDIT: also its funny how Randy is god after having a horrible HW record and winning the title. Hes now seen as one of the top guys, how come Matt doesnt get the same treatment?