The one and only reason that 100LL hasn’t already been banned is that up until now there was no alternative.
As for California, the state has banned new internal combustion cars as of 2035 even though the state neither generates enough electricity nor has anywhere near enough charging stations to support such a move and hand waves away such objections. 17 other states are likely to do the same.
You can expect a ban on 100LL in the very near future and there will not be a 13 year period to switch as from the point of view of the state all the industry has to do is stop making 100LL, start making something else, and use the existing distribution infrastructure.