Finland and Sweden already have a mutual defense pact so neither would join NATO without the other. I think they both probably will, maybe after Kiev falls or some larger offensive is launched. I think Russia really miscalculated here on just how much the world would care about their invasion, I guess when you spend too much time in Syria you just get the impression that people don't really care about wars all that much anymore. It doesn't really change Russia's security situation though, they never had that much influence in Finland compared to the west and it's not like NATO just needs Finland to finally invade.