We still don't know the cost of the subscription, though.

There's good news for 2018 Cadillac CT6 owners because the automaker is extending their Super Cruise service by one year. While it's good for them, there's still the open question of the cost for the driving assist's subscription.

"As a gesture of appreciation to 2018MY CT6 Super Cruise first-time owners in the U.S., last year we made the decision to provide them with a one-year complimentary extension to their Super Cruise service once their initial three-year plan expires. These owners have been extremely helpful adopters of this technology, actively providing us with suggestions and feedback on their experiences with Super Cruise," Katie Minter from GM Product and Brand Communications, told Motor1.com.

Gallery: Cadillac Super Cruise Update

The Super Cruise tech available some current Cadillacs and other future GM models requires a vehicle connectivity plan. Buyers get the first three years free but then have to pay a subscription fee. However, the company hasn't yet publicized the price to retain the functionality.

Cadillac delivered the first units of the CT6 with Super Cruise in September 2017. Before this one-year extension, these customers were coming close to needing a subscription for the tech.

If an owner opts out of the subscription, then the vehicle only loses the portion of Super Cruise that allows for semi-autonomous driving. Safety features like lane-centering and adaptive cruise control remain available.

Super Cruise is an option on the 2021 CT4CT5, and Escalade. GM will make it available on 22 models by 2023. The Chevy Bolt SUV will be the first non-Caddy to offer the tech.

GM is reportedly working on Ultra Cruise as a successor to Super Cruise. The even more sophisticated tech can allegedly handle hands-free motoring on select highways and city streets. It's not currently clear when the system might be on the market, though.

Gallery: Cadillac Super Cruise