The good news is there is a solution, an unleaded Avgas, I have seen, smelled tasted.....well almost.
It has passed all the required FAA testing just recently, I am a few weeks out of touch, but the component compatibility testing was ongoing last I checked. This is very important, as it must be proven acceptable in all the old fuel systems.
I have read the Dixie Labratories test reports, and this unleaded Avgas is a higher performance (in terms of octane) fuel than the old purple 110/145 and is most likely to be known as a 100/150 or 160 as it regularly tests over 160 mon.
It is 100% compatible with Avgas, in any mix you create. Take 999 gallons of Avgas and mix in 1 gallon of G100UL and you have have 1000 gallons of G100UL conforming fuel. Sure it has a TEL content still but it is a conforming fuel certified to go fly. So tank mixing, either in the ground or wing is not an issue.
Just how long it takes to get the piles of reports finalized and ready to produce I can't tell you, but it should be long before 2018 and I suspect maybe before the nd of 2013.
What changed from 2023 to 2018? I suspect they know the answer is here and the dates have been pulled forward for total compliance.
If the Ameicans could bestowe a knighthood honor on somebody for their services to General Aviation, I know one deserving and worthy receipient.
So don't panic about losing avgas, in fact I can't wait to see it go! This new stuff is way better. Ohh yeah, and it has about 2-3% more BTUs so you will pick up a bit of extra range, for me thats about 7 minutes which when Ifr could be a fuel planning deal breaker some times.