In its efforts to come up with a car that blends economy, low emissions and performance at an affordable price, Toyota has decided to use a lean-burn 1.8-litre turbo engine. Meanwhile, the THS-II hybrid system will be upgraded with efficient lithium ion batteries, which will allow the electric motor to deliver greater performance because the cells recharge quickly and hold more power for longer.
Wow, so that's a lithium-ion powered plug-in hybrid with a typical Toyota warranty for under £20,000.... (the current model is about £19,000 over here)
I doubt they'd put this in a Prius, if it compromises fuel economy. They might put it in a Camry, Highlander, or another model where a buyer's more concerned about performance.