Without the space shuttle, ISS has lost its reason to exist. Without ISS, the shuttle would have had no reason to exist.

The ISS orbit naturally decays without regular boosts due to atmospheric drag. I'm hopeful that Starship is fully operational by the time the ISS reaches EOL, maybe a few Starship launches would have enough delta-V to push the ISS up into a graveyard orbit.

NASA has a commercial station program ongoing and they are handing out contracts.

BlueOrigin suggested station does have modules far larger then current ISS, but its attended to be launched on New Glenn, not Starship.