I still want to see a manufacturer come out with a 20L gas engine because it will be cheaper to own than the emissions diesel or the full battery truck.
No, it won't be, which is why nobody has made one. It doesn't work at the 6-7 liter level in pickup trucks, it would only get worse as they got bigger.
I have a friend who is in the grocery business, and owns and operates several single axle box trucks. He had a Freightliner with a Cummins and 26' box that he ran for about 8 or 9 years and put a bit over 300,000 miles on. He had a lot of trouble with the engine, especially in cold weather, so when he went to get a new truck, he took the advice that he ought to get a gas job instead; cheaper to own. He bought a Ford F600 or something to that effect, with the 7.3L gas and 10 speed automatic.
The Freightliner got about 10 MPG, the new Ford gets 5. Now, the Ford has plenty of power, and pulls just as well as the older truck, but half the fuel mileage.
If he runs that truck to 300,000 miles that is about 60,000 gallons of gas, vs about 30,000 gallons of diesel.
At current fuel prices that new gas job is going to cost him $120,000 more in fuel than an equivalent diesel powered truck.
I am no fan of emissions equipment, but that math just doesn't add up.