2016 Toyota Prius to debut on September 9 in Vegas

Ryo Sakai, a spokesman for Toyota, confirmed the launch to Bloomberg, although he declined to elaborate on when the new Prius will enter production or when it will go on sale.

The current-generation Prius hatch was released in 2009, and quickly became the most popular hybrid car yet, with half-a-million sold in its first full year on the market. It rocketed to the top of the sales charts in Japan and was a popular choice in the USA when fuel prices were high.

Despite a mild facelift and update in 2011 demand has fallen in recent times. Sales in Japan this year have reportedly fallen by 31 percent.

In the US, where petrol prices have recently gone as low as 75 cents per litre, Toyota has sold 65,376 Prius hatchbacks to the end of July 2015, a decrease of almost 14 percent on this time last year. Sales are down about 30 percent from this generation's sales peak in 2012.

Locally, the Prius has never been a big seller for the company, but the current hatch is tracking at around the same level as last year — 298 sales to date in 2015 versus 299 at the same time in 2014.

The new Prius is expected to be one of the first models based on the Toyota New Global Architecture (TNGA) component set. TNGA will reportedly help the new Prius to shed around 100 kilograms of weight and lower its centre of gravity.

A report last month indicated that the new car will feature a new hybrid drivetrain with around 110kW of power. The next-gen hybrid will allegedly stick with nickel-metal hydride batteries for entry level variants, while fuel economy is said to be improved by at least 10 percent.

The fourth-generation Prius has so far been spotted, wearing heavy camouflage, on the streets in both Bangkok and San Francisco.