Trubisky's growth was not linear and not always consistently better. However his competition varied so it is not always easy to see a true linear progression in that case.
I am not going to pretend I believe I know enough to say that he for sure won't be elite or he will never be good. No one here is that smart or that knowledgeable to speak in certainties like that. Even pros get their evals wrong. So whatever you think there is still more to come.
What I will say is that I do see the traits in him that really good QBs have. And I saw these traits progress as the year went on.
Pocket presence
Early in the year he looked tentative. You could see he didn't feel the pressure and the game was moving very fast for him. As the year went on he improved dramatically. You could see him move out of the pocket and avoid the rush much more fluidly. The way he was able to avoid people by feeling their presence was one of the biggest changes I saw in him this year.
Extending plays
Mitch always had some ability here and one of the reasons he was drafted. You'd be blind to not see the improvement here and some of the plays he made were absolutely top shelf. If I were an opposing fan and saw some of the things he did on third down it would really piss me off. Again this was an area of improvement as the year went on and directly related to his pocket presence.
Hard count
Mitch was good at this last year. He continued to be good at it. What I'd like to see is Nagy put a piece in there that allows the snap to occur based on a player jumping. I'd also like to see Mitch be able to recognize that and take advantage of the free play.
Shoulder fake
I was waiting to see this happen all year long and we finally got a taste of it in the wild card game. The couple plays he used it helped the Bears score the go ahead TD. I think if Trubisky can do this on a more consistent basis in certain game situations he will piss off a lot of opposing fans and DBs will have to play a little more honestly.
Pre-snap reads
I get some of this but the coaching staff will recognize it more. Based on what Nagy has said he has some work still to get better.
Reading the open receiver
I think this is Trubisky's biggest area of liability. He did get somewhat better, but he will need to improve in this area to take it to the highest level of QB play.
Footwork
It was bad at the beginning of the year but he actually improved in his first three games. And it did get much better as the year went on. He had times where he would regress in spots but there certainly was steady improvement. He just needs to be more consistent.
side note....
Accuracy issues
I am actually not that worried about this. I know he has a tendency to overthrow, but it is typically early in a game and as the game wears on he settles down. I truly think this must be a case of early game jitters and comfort. I think experience takes care of this.
Overall
I absolutely see the traits in him that the best QBs have. In my opinion he has grown significantly but there are areas for improvement. If he can get the pre-snap reads and in play reads need to improve. I do not know his ceiling, but I am confident he has not reached it yet.