Lots more to come with GNSS navigation.
L1C, L2C and L5 are being rolled out. They promise increased accuracy by 2027.
They are rolling out Dual band signals for increased accuracy.
Glonass and Beidou are also rolling out upgrades to their systems.
The ability to use more than one GNSS system improves accuracy and resiliency.
I think GNSS is really impressive for trans oceanic, Polar and outback(Middle of nowhere flying) routes . INS systems are expensive and require calibration. They are still great as a backup.
The Garmin 65 is a multiband GNSS hand-held receiver
My Air-Squitter GNSS info (Single frequency per GNSS system)