I do not work for Toyota Motor Sales USA (TMS, USA) nor do I work for Toyota Motor Corporation (TMC Japan), or Toyota Engineering or Manufacturing North America.... Toyota's dealerships have nothing to do with Toyota beyond being a franchise for the product.
I actually have no idea whether Toyota is getting a diesel in the Tundra or not.
But my educated intuition is: no way in hell. Just like no way in hell is Toyota ever bringing another SFA truck into the North American market.
Just like diesel is a passing fad that will go away once diesel hits $5,6,7 per gallon. Just like we'll all be driving bikes when gas hits $10 a gallon.
We are merely psychologically avoiding the inevitable.