Russia to leave International Space Station by 2020, official says - CNN.com

This will basically mean the end of the ISS if true. The Russian segments are what keeps the station in orbit. There plans initially before budget cuts to add an attitude control module to the US side, but this plan was axed.

Edit: I'm sure Russia will leave their hardware up there, but the rest of the partners don't have what they need to maintain it. Plus, NASA is currently lacking a spaceship right now. lol