How to dispose it was always gone be by dropping it into the ocean.
The European have given up even providing cargo shipments, instead providing the support module for Orion. All the core life support and power modules are US.
Simply put, what the US decides is what the European and Japan will follow along with.
The Russians make grand claims about how they can split of their part of the ISS and run their own station. But the Russians claim a lot of things. Non are actually going to happen.
Neither Musk nor Bezos would ever want to buy it, and almost certainty nobody else would either.
And if you think Musk or Bezos could make it more of circus then it already is, you have not been paying attention. The ISS storyline over the last couple years is closer to Tom Clancy novel then a science project.