Roscosmos has announced their ISS partnership will end in 2 years
This might have been seen as an indication that the new administration at Roscosmos was in a more cooperative mood. Any such hopes were dashed on Tuesday, when Borisov announced that Russia would not be renewing its current commitment to the ISS, which ends in 2024. NASA's current plans involve keeping the station occupied through the end of the decade.
It's not clear what their plans are, but the new head of Roscosmos did say this
According to The New York Times, Borisov told Russian President Vladimir Putin that the 2024 date gives his country time as well. “I think that by this time, we will begin to form the Russian orbital station,” he said.
In theory, Russia may want some of its ISS segments back for this "new" Russian space station. That does present a problem, in that we need some of those modules, and a decent chunk of our modules were flown on the now-defunct Space Shuttle.
From a different article in March, it seems like NASA's Cygnus module could be used to replace the Russian boosting capacity. The catch is that the rocket that took it up there (Atlas V) was made with Russian engines and all the ones we still have are spoken for.
Cygnus has previously launched on the American-made Atlas V rocket. But this booster also uses Russian-made engines. Because of that, the Atlas V was already due to be phased out later this decade after completing two dozen more launches. The Atlas V rocket developer, United Launch Alliance, has taken delivery of all the Russian engines it needs for these flights. Although these missions are all booked, one solution may be for Amazon to give back some of the nine Atlas V launches it has reserved for its Project Kuiper satellite constellation. Another scenario involves launching Cygnus on a Falcon 9 rocket, something Northrop and SpaceX would probably agree upon in an emergency situation.
Another potential re-boost solution could come from Boeing's Starliner spacecraft, but this vehicle has not yet demonstrated the ability to dock safely with the International Space Station. And it, too, is reliant upon launching on the Atlas V rocket.
The SLS is still in testing and, given the enormous cost of a heavy lift non-reusable vehicle, it seems unlikely to be used for the ISS.
Could a Falcon Heavy do the trick for another Cygnus, or an entirely new ISS module? Or would any hopes for heavy lift capacity be in rockets not yet built/flown?