I think it will be really interesting to watch indeed.
There's a few signs that Rantanen has been increasingly a product of Mackinnon so it will be quite intriguing to watch how he can do now away from Mack and if those numbers were just anecdotal silliness, or if they were actually pointing at a bigger concern for him.
On the flip side, what can Necas do playing with 2 of the Top 3 players in the world. He was already a Top 10 scorer in the league this year, not exactly playing with chopped liver as the likes of Aho/Svechnikov/Jarvis are great players in their own right, but they also aren't Mackinnon and Makar.
A fun watch for sure IMO.