Just playing devil's advocate; If Smackdown's ratings continue on a downward spiral for another month or two, could you see Fox moving the show to Thursdays or Tuesdays? If not that, I could envision Vince McMahon coming on and instituting another "Wildcard Rule", thus making the Brand Separation worthless for the 2nd time in the same year.
I think worst case they get moved to FS1 permanently and reign as the number one show there for the rest of the contract term.