I dont think any of them are getting sent down.... not sure exactly what the plan is with the young guys.
In terms of outplaying each other.... I think Lacombe is def furthest along in terms of development(as he should be)... kinda like the jack of all trades guy on the back end, can play LHD or RHD, can play PK or PP, and seems like the player that can get pretty comfortable playing next to anyone on the d group. He tends to get slept on league wide (and prob on these boards too)... but no reason he cant become a top 4dmen.
Org seems to really love Luneau, and we dont have any natural RHD outside of Gudas in the line up right now. Im personally pretty high on Luneau, and think he can become a top pair RHD. He added a lot of muscle/weight in the offseason.... and i think his spot is comfortably in the NHL now... he looked comfortable last year in his 7 games prior to his injury... now he looks bigger and stronger, and i expect him to look pretty damn good in the NHL.
Mintyukov would have 0 benefit not being in the NHL , hes big, has a little nastiness in his game... and most of what he needs to improve upon is things he can do at NHL lvl..... i think he has the best shot of being a #1 dmen out of the young guys.
Zellweger is prob the odd man out right now, but i imagine the team will find ways to get him game time.... he was pretty solid last year in the NHL, were just kinda packed on the back end at NHL lvl right now... i agree there isnt much for him to do in the AHL tho(but i think you can say that about all 4 young guys on our backend)
As far as PPQB goes.... lacombe has looked solid in his limited time as QB (i think he had a little time last season because of injuries).... but long term i just think Mintyukov/Zellweger/Luneau have more tools in their offensive tool box than Lacombe.