With an adequate supply of Plutonium-238, and considering the current budget-constrained environment, NASA has decided to discontinue procurement of ASRG flight hardware. We have given direction to the Department of Energy, which manages the flight procurement, to end work on the flight units. The hardware procured under this activity will be transferred to the Glenn Research Center to continue development and testing of the Stirling technology.
In short, this means that the very best we can do without this much-anticipated advance in RTG technology is perhaps one or maybe two low-cost outer solar system exploration missions per decade, and not until at least 2019, when Plutonium production can reach the necessary levels. This is a serious setback for any missions that can’t rely on solar power.
Of course, it would be incredibly interesting to see if a private-enterprise motivation would fill this void. My first thought in that vein would be power generation for prospecting missions to asteroids and moons, where you may need to submerge into a pitch-black crater on asteroid 4660 Nereus, or maybe the frigid seas of Europa. The sun will be weak at best in such exotic lands, leaving a serious need for extra-solar power.
This is the kind of solution an enterprising space exploitation firm might use to further its business goals, and would justify basic commercial research.