Does he still show as much promise as he did when he was drafted?
Well, he was a 13th overall pick.
I think he shows all the promise you would expect from a top fifteen pick, even upper-top 10 pick and will probably go down someday as a 20+ goal, 40+ assist skilled winger, and based on what he's shown lately he will be a three-zone player too. He has some real heart for the game and he's always smiling, so you gotta love his attitude too. His stickhandling and vision are always going to be his best assets. Aggressiveness and consistency his worst.
He'll probably not break the 30 goal or 60 assist marks but I can see him throwing up seasons similar to Kristian Huselius' Flames career. As long as he can find himself on a line with Bennett or Monahan, he will be damn successful statistically. If he's on a line with Backlund, he'll be successful as a reliable skilled NHLer. Basically he just needs a Top 9 opportunity. He's a smart player, he's a skilled player.
Wherever Sven ends up on the Flames, he's going to be a big part of some big moments. He'll always be a step below Gaudreau's insane level, but that doesn't mean he's a bust. At all. Gaudreau is just amazing. That's where you can really differentiate guys who ought to be top ~3-5 picks and top ~5-10. Though Johnny was a #104 haha.