I think it's pretty clear what'll happen.
MT will drop Eller to the 4th line, and if he has a bad game, he sits in the bleachers
I'm really liking the dimension that Prust adds to the 3rd line but in all honesty, other than Eller, who I don't want to see on the 4th line ever again, I can't see any of our other players doing well on that line.
I think Cole's played himself out of the top 9, but you won't be able to get him back to the way he was playing if you put him on the 4th.