I have no idea what they're going to do next year. You just can't have that many rookies in the NHL.
That being said, I truly believe the following players are ready for full time duty in the NHL, whether it be with the Leafs or another team:
William Nylander
Brendan Leipsic
Joshua Leivo
Zach Hyman
Sam Carrick
Nikita Soshnikov
Connor Brown
Stuart Percy
Scott Harrington
Frankie Corrado
Viktor Loov
Leivo, Sam Carrick, Percy, Harrington, and Corrado all hit waivers next year if they don't make the team. If Sam Carrick is resigned he is the only one I believe might slide through. Leivo, Percy, Harrington and Corrado are all either on opening roster or playing for a different organization. I don't think there is any in between.
Nylander, Hyman, and Soshnikov have all shown that not only can they compete in the NHL but that they stand out as regulars. Don't see how any of the three play for the Marlies next year. They won't put Nylander down next year unless he does something off ice that causes a problem, as I'm sure there's not much more he can do down in the AHL. Based on their effort levels alone, Babcock would prefer Hyman and Soshnikov on the team far more than most regulars he is forced to use like Lupul, Holland, Grabner, etc, so they're locks.
Brown, Leipsic, and Loov are waiver exempt so they probably get sent down and see spot duty during injuries until we trade more assets off next deadline and they're up full time. But in reality has anyone watched them this year and thought they don't deserve to be playing full time. It's funny, if they were assets of the Blackhawks, Rangers, Predators, etc...teams that always have one cheap spot to fill and very rarely any prospects as good...these players would slide right in like a Trevor Van Riemsdyk for Chicago, etc. But a really crappy team like the Leafs have too many similar players at similar points in their development.
No idea what they're going to do.