Yup, they will be landing at an airport near you. The speed and efficiency are pretty incredible, but not many people have 250 to 500K sitting around. Check out this article:

http://www.diamondair.com/contentc/prTwinAtlan.htm

They are already flying in Europe with a couple of different diesel powered planes. Diesels just don't go well with light planes because a diesel is pretty heavy.
A small 2 seat aircraft might have a 230 cubic inch motor that burns leaded fuel.
A very common size is 360 cubic inches and those are only 180-200 horses.
The larger piston powered planes run 520-550 cubic inch motors. All leaded. They have very high compression, so the must use lead. That is going to go away though. I think there is only one company left making leaded gas for planes "avgas".
If anyone is up for discussion on where the light aircraft industry is going, I'm up for conversation.
For those of you that don't really think this is a good topic for this board, keep this in mind. Light planes are dirty, dirty for the environment. I love planes, but the technology is WW2 era, and not much has changed. Everything that is cutting edge in small planes is happening now, and it may prove to be the best way to travel 250-600 miles cheap, quiet and with minimal environmental impact.