His deal is up after next season and he probably won't merit an offer sheet if he's still with the org. I think his rights will probably be traded if he's in the KHL next year (or if some tanking/struggling team has a spot for him on the NHL roster). Probably as soon as this summer. But it also depends whether Fedotov is traded, sent to the AHL (he'd likely clear at his salary) or somehow ends up staying on the Flyers.
So I guess the Flyers did not even send him back to Allentown at the end of the NHL season? If Kolosov really wanted to further his career and his place with the Flyers, he would have wanted to battle for time in the playoffs over two older journeymen.