OEM's routinely overrate the mpg's assigned to their vehicles....or they produce those mpg results in unrealistic driving scenarios. The EPA sets the testing standards, but it's the OEM's who actually conduct the tests and submit the results. The system is far from perfect.
If this is news to you, then you should do some more reading in your spare time.
Edmunds EPA Testing
I'd love to see a Toyota gasoline twin turbo, but I highly doubt we'll see that anytime soon on their trucks. Toyota has been heavily focused on hybrid, atkinson cycle and hydrogen fuel cell applications...that is the direction I see them going. Toyota North America's head truck engineer, Mike Sweers, has said repeatedly that they have looked at incorporating turbo gasoline engines into their truck applications, but that there wasn't enough pay-off in terms of fuel economy for most driving scenarios. I think he mentioned some other longterm reliability concerns as well. I see the next Tundra having a Port + Direct fuel injected v8, similar to the technology used in the Tacoma, with a possible diesel option.
It just wouldn't make sense that Toyota would put a twin turbo gasser into one of their most reliable and respected platforms (Tundra) when they still haven't done that with any of their other current offerings.