I think it is pretty clear that in the not too distant future, AVGAS will be dead or prohibitively expensive for GA. The development of an unleaded replacement fuel will lead to a product that is also prohibitively expensive for GA owners & operators as the quantities of it that are made are far too small to be economically viable.
GA engine manufacturers need to stop having bright ideas on going in different directions regarding unproven 'cutting edge' technology and new fuel types and settle for something sensible and sustainable.
I think the only two options for an affordable long term solution are diesel engines that run on JET-A or conventional gasoline engines designed to run on automotive Unleaded 98.