Many people had Horvat as a lock last year but many weren't sure how he would perform with the bigger and faster game. The same is said with Virtanen this year where everything points to him being on the team but we're not sure how well he will perform.
Also, 6 goals in 9 games is incredibly unrealistic for any player so obviously if he scores that many he will stay. He will just need to show that he can handle the pace and play the role he's given rather relied on to score. Scoring can come later.