There was another pretty neat new engine technology when I was a youngster reading HotRod magazine; the
Hot Vapor engine being developed by Smokey Yunick. A lot of magazines gave this engine a lot of editorial space, (Yunick had a great gift for self-promotion) and apparently it came pretty close to production in 1990. There's a ton of internet on this invention and the problems both technological and political that kept if from seeing widespread use.
This story has been repeated time and time again during the industrial age and it's against this backdrop that I think the idea of a radical new engine will always fight for existence. Yes, someday a radical breakthrough may happen, but for way over a century, for the entire lifespan of the automobile as practical and useful transportation, the ICE using reciprocating rod technology has been the easiest to control and produce. (and seal).
http://www.motortrend.com/how-to/hrdp-1009-what-ever-happened-to-smokeys-hot-vapor-engine/