Likely to be a tuned version of the T8 Twin Engine Hybrid.
In an interview with Auto Motor und Sport, Peter Martens, Head of Development at Volvo, has hinted that the S90 Polestar will feature an hybrid powertrain, and will rival V8-powered super sedans like the BMW M5 and Mercedes-AMG E 63.
He said (translated):
Volvo has taken a strategic decision to completely take over our partner Polestar. We build the brand and invest heavily. Therefore, I can imagine that there will be a sharper version of the S90. With the hybrid drive can give V8 engines a pretty tough match.
Finer details on the hybrid setup are scarce at this moment. It could either be a tweaked version of the T8 Twin Engine Hybrid grade of the regular S90 that could output well over 400 hp, or feature the company's new 450 hp 2.0-liter tri-turbo Drive-E engine (codenamed "triple boost") paired to an electric motor, which could produce well over 500 hp combined.
It's unclear if the gearbox offered would be an 8-speed gearbox or a dual clutch unit, but the S90 Polestar is certain to feature an AWD system.
The exterior of the S90 Polestar could feature a meaner look with large intakes in the bumper, rims that could be as large as 20 inches, rear spoiler, sports exhaust system and exclusive paint options. The interior is likely to feature sports seats, carbon fiber trim, paddle-shifters on steering wheel, and Polestar blue contrast stitching.
[Source: Auto Motor und Sport]