Remember that the huge eight-year contract (9 million per season), signed by Subban with the CH, has just ended and he is now free as a bird.
If Subban ever signs in Toronto, it would be really interesting since the Leafs would allow him to come back home, to potentially finish his career. (He is a native of Toronto)
On the list of the most plausible destinations, we also find the Los Angeles Kings, who count on the services of a certain Marc Bergevin, as right-hand man to the DG.