Russia are committed to the ISS until 2020 and have said they will honor that commitment. What happens after that is another matter. They have suggested they might pull out in 2020. But expect that by 2020 the Ukraine crisis will be history, resolved one way or another, so probably depends on what happens next rather than what is happening right now.
The scientists want to continue with the co-operation at least.
And the US is also currently dependent on Russian technology in the form of the RD-180s engines that power the Atlas V, to launch its satellites (including its satellites to spy on Russia, ironically), and not certain that SpaceX will fill that gap.
The US could produce the rockets themselves, but it would cost them an estimated $1 billion and take five years to set up production according to Aviation weekly.