Are gas engines ever going to catch up?

06Fargo wrote:
Our creaky old Cummins powered truck (bought used) seats 4, does about 20-23mpg bobtail and 12mpg towing a 5th wheel trailer at 22,999lbs. It's mileage is somewhere in between hauling a camper and/or towing smaller trailers. 1500 rpm to 2100 rpm in road gear. 1500 rpm to 2300 rpm in climbing gears. It's happy as can be hauling 1-1/2 tons in the bed when necessary.

Nothing I'd like better than to replace it when the time comes with a quiet gas engine truck that will haul 1-1/2 tons, or tow the 5th wheel at 22,999lbs etc and deliver the equivalent $/mile fuel economy in gasoline dollars. I would like it to maintain the hp I paid for at 5000-7000 ft. and not be too frantic in the rpm department every time it sees a hill coming.

Anything coming on the market that will fit the bill?