The Saab 9-5 is long overdue for an overhaul, with the current model first hitting the streets as far back as 1997. A totally redesigned model was rumoured to make an appearance last year but its release was pushed back due to limited resources at Saab and the introduction of the facelifted 9-3. Saab’s parent company General Motors has since confirmed that the car will now make its debut later this year.

Underneath the heavy camouflage of this prototype for the new 9-5 is a heavily revised version of GM’s FWD Epsilon II platform, which is also shared by Opel for its new Insignia range. To differentiate Saab as a premium product engineers will provide a stiffer suspension set-up, a new steering rack and a different range of electronics. The car’s wheelbase will stretch 2.84m, which is up 14cm on the current model, and the overall length will stretch just over 5m.

Engine options will include a range of four-cylinder petrol and turbodiesel units including a biofuel model. There will also likely by an AWD flagship model with a turbocharged petrol V6 displacing 3.6L and developing upwards of 350hp (261kW). Other engines will include a 210hp (157kW) 2.0L unit and mid-level 2.8L V6. A petrol-electric hybrid model is also expected.

The new 9-5 will be sourced from Opel’s Ruesselsheim plant in Germany with production tipped to start in the middle of the year. It will then make its debut at September’s Frankfurt Motor Show as a 2010 model.

The included computer generated rendering shows that designers will be sticking with the avant-garde styling of the original Aero X concept car, and will likely keep the protruding nose, large vents and sculpted bodywork. Other details will include a sleek, coupe-like profile and hatchback rear end. Earlier this month several images touted to be official shots of the car surfaced online. You can see them in our previous story by clicking here.