NASA still cooperates heavily with Roscosmos and American astronauts regularly fly in paid Soyuz seats. The latest one is Johnny Kim who launched in late April on Soyuz MS-27 from Baikonur and will stay on the ISS until december. And Christopher Williams is already scheduled for the next Soyuz mission.
China on the other hand will probably never happen because of the general political climate in the US and this administration in particular.
Also I believe that Russia isn't being paid for astronauts to fly on Soyuz. Instead, cosmonauts fly on Dragon. It's a like-for-like exchange which is mutually beneficial (both countries need the other's cooperation to keep the ISS operational, so these exchanges ensure that can continue if either Soyuz or Dragon are grounded for some reason.)
China on the other hand will probably never happen because of the general political climate in the US and this administration in particular.