It appears that the reason the Subaru WRX STI is no longer available has to do with European emissions regulations . So, perhaps to get the STI back, it will need to be electrified?

Subaru redesigned the WRX a few years ago, but enthusiasts immediately noticed something was missing. The brand’s vaunted STI ...

The STI badge has been dormant for years, but EVs could help revive Subaru's top performance line.