RD-180 are being manufactured continuously last ~20 years. All new, not manufactured long time ago.

NK-33 - from which AJ-26 are made - aren't manufactured today. It's a question if the manufacturing will restart. There are a few tens of them in US. Orbital Sciences has that question in the middle of their table, or close to it.

Russian-American relationships in space trace back to at least 1975, deep Cold War. We're not at that state of affairs just yet. As somebody mentioned on The Space Review, ISS is a front-runner for Nobel peace prize, so let's not jump the gun too early. It doesn't seem to be too desirable for Putin to close that particular relationship.

There is a successor NK-33A engine being produced for Russia's own Soyuz-2-1v. http://www.uk-odk.ru/eng/presscenter/odk_news/?ELEMENT_ID=20... http://www.samspace.ru/news/press_relizy/4228/ (in Russian)

Unfortunately engine itself is not produced. Those are all modifications of existing NK-33.