If the plan really is to wait until next year, it could easily go wrong. Even the players who have not yet extended still have 8 months to do so.
If the Sox are not sold on Montgomery for some reason, I think the plan is to get another starter internally, which means more Houck and/or Whitlock and possibly Winckowski. At the very least, if that is the plan, hopefully they at a minimum backfill the vacated bullpen spot. Ryne Stanek is the best available RP still looking for work...