ICE dead, not so fast
 

The ancient opposed piston layout may come back and fight on.
The lighter, lesser friction surfaces and simpler design do not need the typical four-stroke engine valvetrain, intake and exhaust ports, and complexity of synchronized camshafts and valves.
Electronic control now allows the optimum metering of air and fuel precisely and could take advantage of the design's inherent simplicity and efficiencies.

Opposed-Piston - Achates

https://www.youtube.com/watch?v=_QTfvIfsjJw

https://www.youtube.com/watch?v=Ov73-okhkG0

They say about 4 years from being put in a car. Is this the Elio motor?

It would be interesting to see more technical data on the engine. It obviously has some benefits and I'm sure some drawbacks.

"Simpler design" should have a disclaimer. It's interesting that you could possibly do away with camshafts, but without additional hardware you now have a fixed valve timing engine. I foresee most solutions to this being more complicated and potentially more failure prone than a balanced rotating shaft.

Plug-in hybrids (or EVs with "range extenders) are certainly one solution to battery limitations, but ICEs today are large and complicated, and take up a significant portion of a vehicle. Anything that can downsize the footprint without sacrificing efficiency would be great.

The only 2 stroke engine I have seen that even have a shot at possibly meeting emissions in the US use exhaust valves.

With direct injection and a cat you shouldn't need them, only issue is you would have to run "lean" to burn the oil blow by or have a trap of some sort

Modern snow mobiles run oil injection separate from the fuel.
The exhaust valve engines appeared to allow for more power at full throttle and delay the exhaust rejection to allow more time for better fuel burn at part throttle.

The part throttle or variable valve issues could be solved by teaming it with an electic propulsion and running the motor at max power just to recharge batteries. A setup like that should be allowed to have higher emissions while it's running because maybe it only needs to run 1/2 or 1/3 of the time.

Achates, Cummins and US Army
 

Gasoline and diesel (possible multi-fuel) Achates engines for the foundation of Future Fighting Vehicle for the US Army.

Achates Power Wins $14 Million Military Engine Project

us-army-awards-contracts-for-future-fighting-vehicle-designs

Different opposed piston engine designs
 

Opposed piston engine in a hybrid setup.

https://www.youtube.com/watch?v=jA0DZXpkQV0

Another engineering group and their opposed piston/opposed cylinder setup.

https://www.youtube.com/watch?v=9Gcaoel6QFY

Even weirder, a rotating opposed piston engine!

https://www.youtube.com/watch?v=kHXKNpXoQUo