All CHL players are eligible to play in the AHL or NHL following the completion of their season, regardless of whether they are old enough or not. But one would hope that Rychel, Dansk, Bjorkstand and Anderson's respective teams would all have long playoff runs.
NCAA players can only play in the AHL once they have gone pro. The only CBJ draft pick graduating is Martin Ouellette, who may get an amateur try-out in Evansville to see how he can do playing pro hockey, but not much is expected of him despite how well he's played this season. I would be surprised if any of the other CBJ NCAA draft picks left early after this season.
Players from Europe can come over once their team's season is completed. Wennberg's team should go deep in the SHL playoffs, so don't count on seeing him. Dano's team won't be in playoff contention, and Zaar's team could make a push for the Kvalserien, but it's unlikely. Both of them could come over to play for Springfield, but rushing moving overseas and adjusting to play a completely different style of hockey on a difference size ice surface isn't easy for a 19/20 year old and Springfield's coaching staff likely will be more focused on the team winning than helping prospects adapt. So, I wouldn't count on seeing any of the Euro prospects until next season.