As much as we've all expected a retool this year and a step back, I feel like we're actually pretty well off moving into the next couple of years. Our core is all in their prime (Petro, Tarasenko, Schwartz, Parayko) or entering it...then we've got several nice young players who can add to that (Edmundson, Fabbri, Allen), and some vets with some tread left on the tire hopefully (J-Bo, Steen, Stastny, Berglund). If the next wave of players (Branford, Barbashev, Dunn, Walman) can step in and become legitimate top-4 d-men or top-6 forwards, the Blues might be right back in the Conference Finals in a couple of years (ready to be blown out by the Oilers).
A D-core of Petro, Parayko, Edmundson, Dunn/Walman (if one can 'boom') and Bouwmeester is every bit as intimidating as Subban, Josi, Ellis & Ekholm...and the forward depth for St. Louis should be enough IF they can land a top-6 center somehow.
Armstrong has plenty of flexibility if he can dump the likes of Yakupov, Lehtera, Gunnarsson, Upshall & Brodziak. The latter two guys (along with Perron, Berglund & Steen) have been awful in the playoffs and should be able to be replaced internally no problem.
As far as Perron - I'd make him available to Vegas, and give his protected spot to Reaves (despite the boneheaded penalty he took leading up to the Ellis goal). He's only got one year to UFA, so that alone may dissuade the VGK from choosing him. And even if they do, I'd prefer to give his spot to Agostino/MPS and move on from DP57. Guy is too slow and ineffective in the post-season when his time & space are taken away. Plus, the offensive-zone penalties would drop by about 70% with him off of the roster.
All in all, I don't think this club is too far off from being a contender. A UFA or trade-deadline acquisition of Tavares would make them favorites in the West for the next-5 years in my estimation. That would cure a lot of what ails this club. And if we could stop taking too-many-men penalties in addition to somehow landing Tavares, they'd be almost unstoppable.