IMHO the D should stay as-is until Keith comes back. Svedberg might be in a lull but he hasn't been as bad defensively over as many games as Daley or Runblad as-yet (Hjammer's bad game seems more like an outlier) Once Rosie comes back, the 'hawks need to evaluate Rosie--after all Rosie was Andrei Zyuzin-level worthless for all of 2014 and all but the Minny series of 2015 (and that was because Keith was carrying his carcass). If Rosie looks better than any of the rookies than yes, send the odd-man out down for playing time.
Once Keith comes back again, reevaluate who the odd-man out is and if it's a rookie, send them down for playing time. If it's Rosie it's not necessary.
Still, as the rookies go I think TVR and Gustaffson have looked better than Svedberg, and all three have looked better than Runblad.