MLS is not supplanting ILS, in fact MLS will be dead and buried within a few years. It's not that funding is going to run out, it's that nobody manufactures the system any more, and the current one is about to reach it's end of life. The main benefits of MLS (smaller sensitive area in CAT II/III ops) have largely been replicated by the new 32-element array ILS localiser antenna on the market now anyway.
A standard RNAV GNSS (APV Baro VNAV) approach can't get to the same decision height as a CAT I ILS, so that won't do it either.
GBAS will, especially when CAT III certification is granted.
However, even new aircraft coming out of the factories now are noit fitted for GBAS, so ILS will be around for another 30 years at least.