I've heard they are looking into diesel, but it is purely for fuel economy. It won't be a "fun" diesel. Think the 4cyl that the Prado gets in other markets.
Depending how they did hybrid, it could be good. The new LS500h has a pretty slick hybrid setup that gets that big boy to 60 in 5.4 seconds with a 3.5L gasoline engine.
"The new LS 500h is equipped with Lexus’ Multi Stage Hybrid System, a breakthrough technology that enriches the hybrid powertrain performance experience and is also seen on the all-new LC. The system adds a four-stage shifting device to the Lexus Hybrid Drive combination of a 3.5-liter V6 gas engine and two electric motors. The result is more direct response to driver inputs while maintaining the characteristic smoothness and efficiency for which Lexus hybrids are renowned.
In a conventional full hybrid vehicle, engine output is boosted by the electric motor via a reduction gear, but with the new Multi Stage Hybrid System the power from the V6 engine and the hybrid battery can be amplified by the four-stage shifting device, allowing much greater drive power to be generated when accelerating from stationary and achieving a 0-60 time of 5.4 seconds.
The design of the system places the multi-stage shift unit immediately behind the power split device, on an axis aligned with the engine crankshaft. Although the unit has four speeds, the D range has a simulated shift control pattern that delivers the feel of driving with a 10-speed gearbox. As vehicle speed rises, engine speed increases with a linear, direct and continuous acceleration feel, free from the “rubber band” effect witnessed in some continuously variable transmissions. In the 10th gear range, the CVT control allows for high-speed cruising at lower engine revs for quiet, smooth and fuel-efficient performance."
Toss a transfer case on the back of that transmission and we'd have a 27mpg 4Runner that does 60 in 6.5 seconds... The 4400lb LC500h does 4.7 seconds to 60 and 35mpg highway. 27mpg and 6.5 seconds to 60 seems completely doable in the 4Runner chassis.