Having sat back on this thread since it first appeared (ok it may be a wind up !) I will give my opinion for what it's worth
There have been inventors thinking up new designs of internal combustion engines ever since the first one was made (and that was debatable who first made it ).
Regardless of anything else all these different types of engines all still use fuel that is rapidly running out, and I have yet to see any novel designed unit powerful enough to propel a car at a reasonable speed that does amazing MPG.
I had some old 1920s books that showed most of these "different" types of engines, although most couldn't be made to work for more than 5 minutes because of the materials available in the period, never the less the ideas were there.
A lot of these overcomplicated masterpieces (although clever) have a lot of reciprocating parts that absorb power through frictional losses so are counter productive and also expensive to tool up for and make and test and develop !
The conventional engine as we know it in its modern guise ain't doing so bad as in the last few years some cars are probably doing twice or more MPG than they were 20 or 30 years ago for a given cc vs speed. (OK I do know modern cars are more aerodynamic as well ! )
The only ICE that I personally think has any future is the one that can increase or decrease the internal CC when needed. But it still needs fuel !
After saying that I don't decry all these innovative thinkers working in their sheds as life would be very boring
