One inch would be imply a sensor size almost 4 times bigger (actually 1.9**2 = 3.61 times bigger) which would require a much bigger lens (or lens with different focal length, or both) and probably bigger body and more battery consumption and much more expensive. it would be a totally different camera.
Maybe they could do add another series but, I have no idea about business, marketing, etc. So, I do not know if this would be a profitable action for them. But, If they improved only battery consumption, I do not believe that current owners of 11 will upgrade to 12 though. At least I wouldn't.
And the price of 11 could drop at the same time.
Totally! Insta360 did it a couple years ago with the ONE RS 1-inch Edition, which could be purchased as a camera module upgrade or as a complete modular camera system unit. It’s sad that Insta360 didn’t develop that system any further and appears they no longer support it either. But I do remember that sensor had a shallower depth of field and because it was fixed focused out to “infinity” it meant a good amount near the camera was not in focus. This made it difficult and even useless as an action camera for most people and uses. It’s a struggle to find the balance of sensor size, battery performance, low-light, and small size with light weight.
Perhaps, as you suggest, we will one day see a complimentary line that goes along with the Hero Black series that is different in this way. It would be neat to have a camera ecosystem that all use the same battery and have different feature sets for different uses. We may want that critical wide shot from the traditional full sensor Hero, but also have a use for a better performer in lower light with a more linear angle of view.
For all we know, the new camera could have a new sensor that brings other benefits to the table. Judging by the rumored specs, that does not appear to be the case. As much as I love my GoPro cameras, I am totally amazed by their lack of any innovation in this segment while its main competitors, DJI and Insta360, have smashed it out of the park with ingenuity, albeit while sometimes falling short in their implementation.