Not that he was slug earlier in his career, but Perron looks like a late bloomer. I think he'll continue to play at the high level he's been at since returning to the Blues in 2018. Dunn is only 23 and I think he has plenty of room to grow _ that's assuming he's back in St. Louis. And there's no reason to think Schenn won't return to his 2019-20 level. (Remember, he was an all-star in '17-18). I think the outlier was his lower goal production in '18-19.
As for players who can take the next step forward: Thomas, Kyrou, Blais would head the list. I've mentioned this before: Blais was on a 20-goal pace after 20 games last year, then had injury issues. Also, Sundqvist was on a 20-plus goal pace, then had injury issues.
But keep in mind, some players will have strong seasons, some will struggle for whatever reasons. It's just the nature of the business. Like a baseball batting order. In any given year, a few players may have career years, a few may have off years, a few may be around their career norm. For a myriad of reasons.
Last year for the Blues, they had a lot of players either exceed career highs in goals or points, or come close. That helped them overcome the loss of Tarasenko for the last 61 regular season games with their highest scoring team (in terms of average goals per game) since the '94-95 season. It may be asking lightning to strike twice to think that can happen again without Tarasenko for a large chunk of games.