The only real alternative to 100LL in Europe are Diesel engines using Jet A-1. One has trouble getting 100LL fuel south and east of Germany/Austria even now - and I can only see the decrease in sell of Avgas, not an increase. I think the chance of getting a new gasoline on the market in Europe is highly unlikely, if not utopic.
If the new avgas being talked of here gets up and going I don't see any diesels coming out of the US for a while.
Sadly, USA and Europe are light years away in the GA terms, but that's the world we live in.
Here in lies your problem, the GA market worldwide is still driven by what happens in the USA. Your choices in Europe are going to become less and less unless you are prepared to pay for expensive STC's to fit diesels from the likes of Thielert and Austro to your US made aircraft.