sorry, i just have a silly question: what would it take to send new probes out there? voyager 3 and 4 for example to follow the same path (more or less, sans planet alignment) V1 and V2 followed, but with better hardware of course.
https://voyager.jpl.nasa.gov/mission/timeline/#event-a-once-...
But you'd still have to fly for ~40 years to get to where they are now, and they'll keep on flying during those 40 years.
We could use more investigation at Uranus and Neptune, but we'd get much more out of extended orbiter missions to those rather than another quick flyby. A Uranus orbiter is currently one of the higher priority missions in planning, and there's a launch window for a Jupiter-Uranus slingshot in 2034 or 2035.
(What I wonder is, how much planning do these things need? Why can't we just launch another copy of Cassini to Uranus and skip all the expensive design? You'd need some changes to antennas and power supply for a more distant planet, but the scientific instruments and computing platform should just be reusable designs.)