Pretty sure the overall wind resistance between the Tacoma and LC/GX550 will favor the Tacoma. The LC/GX is taller and wider plus it will weigh more than the Tacoma.
Wind resistance is the factor that kills mileage the most. For reference, doubling a vehicle's speed equates to roughly 8 times the hp needed to move it down the road.
The original 27mpg estimate was a fabrication by Toyota. It takes a certain amount of hp to move a vehicle this size down the road (hp takes fuel) and the current battery pack only has about 3 minutes of work available at its advertised full 48 hp. The battery pack might help out a bit in city driving, but it's just about useless on the highway until it's time to pass or pull a steep hill for a few minutes.
I'd be happy with anything above the current 14-15 mpg I get in our 100 series, but I'd gladly buy another 14-15 mpg Toyota if I get the same reliability and toughness our 100 series has delivered after 326,000 miles and 20 years of ownership.
I'd wager that real world mileage at 65-70 mph will be closer to 20-21 mpg on a good day.