The Obama administration had been planning to "deorbit", aka destroy, the ISS as soon as 2020. They just announced intention to keep it going until 2024. This is just intention, they don't have funding passed thru Congress yet. But they probably will be able to get the funding.
Seeing as how they only got the ISS fully functional last year, it makes sense to operate it for a while. It cost $100 billion to put it up there. Planning was of the "if you build it they will come" type. Result, nobody is using it much. But the kind of things you can do in the ISS takes time to set up and do, time being years. Lot of things will get started now that it looks like the ISS will be aloft long enough to do them.
Cost to keep it running is $3 billion a year. It needs a steady launch of supply vehicles bringing up food, water, air, science experiments. It also needs the occasional push. It flies so low that there is still some air drag to slow it down. The shuttle missions used to burn some fuel to push the ISS up to compensate for the drag. Now that the shuttle is retired, they will have to do it some other way.