I think it is interesting that so many people are looking for better mileage in these trucks. Better mileage comes at the cost of other desirable features. There are 3 main ways that a manufacturer can get higher mpg; Weight, aerodynamics, and drivetrain efficiency.
Weight = lighter frame, lighter bumpers, lighter (i.e. softer) rear springs, etc. = less durability. So you swap out the bumpers, box and reinforce the frame to support the bumpers (and heavy stuff we bolt to them), put on heavier springs to support all the stuff in the bed.
Aerodynamics = airdams, long rigid "mud" flaps, long pointy overhangs= stuff that gets ripped off either intentionally before or accidentally during offloading, then a roof rack with a bunch of stuff gets stuck on top anyway.
Drivetrain efficiency = lighter components, either lower output or more complicated engines, smaller lower rolling resistance tires etc. = light stuff breaks, complicated engines are harder to fix in the middle of nowhere, low output ones can't hual the load, the OEM tires suck so we replace them.
I'm all for fuel efficiency, I have a rule that every new vehicle I buy has to get better mpg than the one it is replacing, but lets be realistic. Anything that Toyota does to improve mileage on these trucks is going to either be negated by the load, swapped out, or cursed for breaking by 90% of the people on this forum.
It would be nice if our Tacos could make 500miles on a 20gallon tank, but lets call it what it is, a truck. By definition of use a truck is not going to get good mpg, but it can be more efficient at hauling the load we expect of them.
All that is to say, give us a turbo 4 cylinder diesel all ready. Oh ya, fix that stupid low hanging exhaust crossover pipe too