I think he's definitely going to find more aspects to his game, but I'm not convinced he's going to develop tools that he doesn't really possess now. I see him developing the things he's already pretty good at: defensive play (I thought he was a very defensively-minded center when I saw him in junior), net-front play (especially on the PP), the odd bit of physical contact, skill play in small doses. In essence, a Brian Boyle type player.
He's not much for the following, IMO: stickhandling, passing/vision, shooting from any kind of distance. I don't see him suddenly taking a great leap forward in those areas, but if it happens, I'll take it.
Hopefully his well documented incredible drive will help him maximise any development there is to be had. He may be a Boyle type player, but unless he totally stagnates, he'll be better than Boyle.
The problem with this discussion is that a lot of his detractors keep making comparisons to players who are simply more physically developed versions of what Rasmussen is now - and a lot of his biggest fans are projecting significant growth in multiple facets.
I still see him at this point as I have done for a long time. Panning out to a sort of uber-holmstrom, who is bigger, will be even stronger in time, skates a fair bit better, can alternate between center and wing, wins face-offs, and is defensively very sound, who is capable of the odd surprising bit of playmaking, thought its not a forte. If he stays injury free, I see him as a good second line foil to a line also comprised of a 2 way playmaking type and someone who skates like the wind.
He could certainly be a very nice fit with saw Veleno and AA / Veleno & Zadina / Hirose and a younger and slightly better Helm type.
I think if he stays injury free, he'll probably peak as an average 50-60 point player with similar goal/assist split who is an absolute BEAST on the PP and solid enough elsewhere that you don't have to hide him. Sort of 2nd/3rd line interchangeable centre who is 1st line PP and can fill in on PK (REACH!) reasonably often.
The key thing for him is more strength on that frame - at present he lacks the strength to have much in the way of acceleration and the strength to drive the net or play net front nearly as well as his frame/skillset suggest.
I still like the pick because I think he'll be relatively unique and also because for years Detroit has been killed by LARGE centers who skate reasonably well and have good hands. I think in the fullness of time he'll also give opposing teams FITS in the playoffs
It has to be said, his hand-eye is still incredible