There's no word yet on if Rusev is interested in leaving WWE, but it would not come as a surprise to many as it's believed that he is unhappy with his position in the company due to some of his comments in media interviews and on social media.
Rusev is currently away from WWE as he recently requested some time off. There's no word yet on when he will be back, but it's likely just a short hiatus. Meltzer speculated that the hiatus has to do with Rusev being unhappy. It was also speculated that WWE could extend the length of the contract due to the time off by freezing it, which they do when a talent is out of action with an injury.
Rusev would obviously generate interest from some of the top wrestling promotions, including AEW and NJPW, as was speculated by Meltzer, but that's not confirmed. Depending on Lana's contract status and future with WWE, there is also the potential for the Rusev - Lana package deal in other promotions.