Continental appear to have decided that the "new" AVGAS will be 94UL and are starting to prepare for its introduction. They have an advantage because the Continental IO550/TSIO550 series seems to do better on unleaded gasoline than the Lycoming IO540/TIO540 series. Since about 2/3 of all avgas sold today in the US goes into one or the other of these engines IMO what works best for the big block 6 cylinder engines is going to be the final solution. Swift Fuel and GAMI are working on a true 100 Octane no lead formulation but it is hard to see how they will be able to make it work at a reasonable cost per gallon given the low volumes. I was a little shocked that US refineries do nto even consider AVGAS as a gasoline product but class it as a specialty chemical. The big advantage of 94UL is that it uses the existing refinery processes and distribution system, this alone has got to represent a powerfull reason to go the 94UL route.