Subaru's Impreza was redesigned around the Subaru Global modular platform in 2017, but the high-performance WRX and WRX STI models trace their roots to the previous-generation Impreza launched all the way back in 2012.

They're long overdue for a redesign but the wait could be worth it if a new report proves accurate.

Forbes reported on Saturday that the redesigned WRX and WRX STI will arrive in 2021 and that the latter will benefit from a tuned version of the 2.4-liter flat-4 that debuted in the 2019 Subaru Ascent. The engine, code-named FA24, delivers 260 horsepower and 277 pound-feet of torque in the crossover SUV but in the WRX STI, it will reportedly deliver 400 hp and 361 lb-ft with the aid of a turbocharger.

2019 Subaru WRX STI S209, 2019 Detroit auto show

2019 Subaru WRX STI S209, 2019 Detroit auto show

The most powerful WRX STI previously launched on the market is the limited-edition 2019 WRX STI S209 which generates 341 hp from a 2.5-liter flat-4. However, this model's engine is related to Subaru's much-loved EJ20 2.0-liter engine which was discontinued last year.

There was no mention of what engine will power the WRX and whether electrification will play in a role, which has been previously rumored. One possibility for the WRX is a new 1.8-liter turbocharged flat-4 Subaru unveiled last year in a prototype previewing a redesigned Levorg wagon due on sale overseas later this year.

As for the styling? Subaru is no longer expected to use the Impreza's sheetmetal as a starting point. Instead, the next WRX and WRX STI will likely pull plenty of inspiration from the Viziv Performance concept shown at the 2017 Tokyo Motor Show.

Subaru Viziv Performance concept, 2017 Tokyo Motor Show

Subaru Viziv Performance concept, 2017 Tokyo Motor Show