When GPS receiver systems add L5 support, my understanding is that LPV type performance will be available when not in an SBAS SV. These GPS systems will also support SBAS. There is not a full constellation of GPS satellites that support L5, so I would guess it is still some ways off into the future. One thing for sure, any new GPS will be more expensive than the current systems and there are none on the market right now. L5 is a new GPS frequency. Current systems use the L1 frequency. With both L1 and L5, the receiver will be able to determine corrections for ionospheric delay without SBAS correction.
So even outside SBAS volume the GPS can fly LPV if it can combine L1 & L5 to get a correction without receiving SBAS signal?
However, I think legacy non-SBAS TSO129 can’t fly LPV no matter what one does with the quality of position or correction: what they lack is “LP performance” with angular CDI sensitivity, although if one can keep neddles in middle it should be identical to LPV on new boxes !
