That's the setup discussed in this article. My impression was that the ion engine coupled with a nuke power plant was on the front burner for future deep space missions. Does the deferral of JIMO mean the research isn't going ahead with that combo or is the JIMO mission on hold for other reasons, like budget considerations.
Not that those program decisions are necessarily bad. I just wish this country had the vision and guts (like it used to) to do both. My guess is that some limited technology development will continue for awhile, anyway, but without a high profile mission as the driver, those efforts are usually limited and often fizzle out (like the SP-100 effort back in the 1980s).