There is a chance, but it really depends on how well he does in the Liiga next year. If he looks like a legit defenseman at 21, he will likely be signed to an ELC and play on the Marlies for 2021-2022. If he sucks, then he's probably nothing and I think his rights expire next year anyways. So make or break for him.
There has never been room for Rasanen on the Marlies. We have Lindgren, Duszak and Hollowell. They are not going to have a 4th younger guy in the mix. At best he could have replaced one of them, but playing everyday in the Liiga makes a lot more sense. The only thing is that he should have done that 2 years ago instead of going to a team in the KHL which rarely plays young players (Rasanen is 3rd in U24 GP since Jokerit joined the KHL; one of them is Tolvanen and the other was a defenseman who only played 20 more games but fewer minutes per game).
It will be easier to fit him in the 2021-2022 lineup when Lindgren/Duszak/Hollowell should be capable of playing a larger role or are in the NHL, Rasanen has had a full year of pro under his belt, and there is a spot open for him.