We know about the talk regarding Kreider to Colorado at the draft that never materialized. So you'd have to think they could circle back on him. I doubt adding Burakovsky over the summer means they'd no longer have interest. Might be too early for the Avs to start chasing down rentals though.
St Louis is an interesting one. Kreider fits their style of play and can solidify that top-six pretty nicely for a run at another cup. I'm sure the Rangers would be thrilled to add a guy like Kyrou who can eventually be a Kreider-like player down the road, but he falls pretty squarely in that vein of Sergachev with McDonagh -- meaning he's just a pipe dream that fans will latch on to.
Sure, maybe the Rangers could help the Blues free up some cap space to sweeten the deal, but usually those deals happen over the summer. I don't see anyone on their roster other than Steen or Sanford that they might like to dump and they're both signed through next year. Sure the Rangers could buy either of them out, but that'd be $10M in dead space next year between Shattenkirk, Girardi, Spooner, and one of those guys. Plus I think Steen, despite not being the player he used to be, is well liked in the locker room. Doubt the Blues are in a hurry to muck with locker room chemistry.