Williams options for next year are Cosworth(yay old school), Honda(less old school) or Lexus(re-badged toyota).

Williams has won a billion titles with Cosworth, and with next years new v8's, it would be especially nostalgic, as it would be reminiscient of the old Cosworth DFV motor that led Williams to its glory years. Honda and Williams had 3 championships together, but they had a falling out.

I doubt Reubens will go to Toyota, Ralf and Trulli's contracts are locked in.