I think the longer he goes without an extension, the better the chance that he's gone to NA after the season. I think its the same situation for Shestyorkin. There's about two weeks until the playoffs, and both are out of contract. I think both are coming over.
Rykov could be in line for immediate NHL minutes. He's closer to the NHL than Hajek or Lindgren, who might never be good enough to play in the NHL. McQuaid is a UFA, so that opens up at least one spot. But we still have 7 NHL defensemen, besides that. I think they might clear out Smith. He sucks, and shouldn't be taking time from an NHL ready prospect. One of the offensively-inclined RD's could also go. There might be room for Rykov on the NHL team immediately. If not, he should be the first call up in the AHL. I don't see that as a bad option for him. He's going to be the next prospect into the NHL team, if he joins the organization after the season.
If Rykov returns for another KHL season, he opens the door to joining the team at the same time as Miller, Lundkvist and Reunanen. I don't think he's so accomplished that he couldn't use another KHL season, but his game is rounding into NHL ready form towards the end of his KHL contract. He could probably step into the NHL now, and hold his own.