As we saw in the last few launches, cold gas thrusters (the F9 first stage uses nitrogen for recovery maneuvers) seem to be sufficient to maneuver the stage before fins engage.
But yes, Superdracos could be used to help land the first stage but are not needed since the center engine can throttle down far enough to allow landing (and that's already with a much lowered thrust being a single engine versus nine). The second stage, however, has a single engine already, so would need to throttle down nearly an order magnitude more than the first stage center engine. In that case, Superdracos would make sense.
In fact, auxillary landing engines (perhaps SuperDracos) for the second stage are shown in this 2011 video from SpaceX:
Elon Musk mentioned they decided to hold off on second stage reuse for the time since a kerosene/oxygen vehicle doesn't quite have the performance margin to make it worthwhile for high-energy payloads to geosynchronous transfer orbit, but SpaceX recently won a contract from the Air Force to help develop their new high-performance methane/oxygen Raptor engine (eventually for their "BFR") for a Falcon 9 or Falcon Heavy upper stage. Maybe that's just the Air Force talking, but it could mean that they intend a higher performing upper stage, and it would be consistent with previous SpaceX statements if this stage were reusable like shown in the above video, and probably would also require auxiliary landing engines to have low enough thrust to allow reliable landing.