Watching Provorov this season, I think he has a lot more upside left.
Last year he was adjusting to the NHL and focusing on defense first.
This year he's been stretching his offensive game, carrying the puck more, spending time deep in the O-zone and shooting. He's on a 34 ES point pace in his 2nd season, after 25 as a rookie.
However, his defensive game, especially his focus, seems to have suffered from that increased focus on offense.
The next two seasons I'd expect him to integrate both aspects of his game, improve his shot, and his feel for offensive flow and take a step up to the elite level. He has a chance to be a special two-way defenseman who excels over all 200 feet. 30-40 ES points a year plus whatever PP points he can garner on PP2.
But RFA deals come in well under FA deals, so I'd think they could get him for 8 years, $6M or so.
I'd certainly lock him up, I think his downside is what we already have seen from him, and that's a $4-5M RFA, so chances of a significant overpay are small.