Going beyond earth orbit GPS is useless.
Ah Krump, but we never know what single vital element might be uncovered in space travel that might benefit nav of all sorts
We might have some technology that would allow interplanetary journeys but first they take a very long time even at 12k/S it takes months to get to the nearest planet. Not exactly the most entertaining vacation. Then what do you do when you get there? Stare down from orbit? Ooh ahh..
GPS by its name is only for earth navigation. It doesn't or wouldn't help for interplanetary travel.
Could we set up interplanetary beacons that work like GPS? Sure but why if no one is using them or there is no demand to travel outside Earths orbit.
Try back in say 500 years then you can one up me in this discussion.