It’s unlikely GPS will be entirely replaced. Lots of platforms and equipment use the precise timing of its signals to do all of the functions they need. We already have requests for PNT in GEO and cis lunar space for accurate positioning on scientific, military, and commercial vehicles, which cannot be done from LEO. However, PNT data on Earth can be backed out of starlink signals as an unintended use of their service, but I believe that signal still requires GPS data from the aft antenna. There are at least two other programs actively developing PNT from proliferated LEO as well. The additional platforms providing PNT augment GPS signals to improve signal accuracy, minimize jamming effects, and provide redundancy to minimize adversarial ROI for attacking a GPS satellite.

Full replacement of GPS is possible, but won’t happen in this generation of satellites. My guess is we will have layers of PNT from mobile terrestrial ground beacons, proliferated LEO for resiliency, legacy MEO with the most accurate timing, and a persistent GEO layer for omni-present coverage to lower orbits and region-specific interests such as indo-pacom.