There are no plans at the moment because it is not even clear how long will current fuel supply last. NASA engineer today said "maybe 20 years, roughly speaking", my back-of-napkin math says that it could be up to 30 if everything goes great. It will depend on exact schedule of observations, number of unexpected transient observations and solar activity. Computer simulations of its orbit and solar wind pressure have some error bars that will be corrected once we get solid data. It also has funding for only 5 years of ground operations right now. Once the mission get extended and we have solid understanding of how it behaves in space we could think of designing refuelling mission. It has fuel port so it is possible in principle, but I don't expect any concrete plans within 10 years.

I guess the videos I watched made it seem more sure than it is... at the very least they left themselves open to the possibility of it if it makes sense to do.