In short:
- No suitable KBO found yet
- New photo's June/July Subaru Telescope
- Possible new photo's October Magellan Telescope?
- Possible new photo's Hubble Telescope?
This is why folks need to support SLS. Such large LVs will allow something like JIMO--or even larger, more time to pick and chose--this is where nuclear electric shines.
Simpler flyby probes we have settled for in the past just don't have much reach once they have passed the initial target.