MMW: Coke Zero is going to replace regular Coke as the primary Coca-Cola product
Evidence: With the recent rebranding of Coca-Cola, they really seemed to lean into using Coke Zero in place of regular Coke, making the branding look closer so that they are almost indistinguishable from each other. If Coke Zero tastes almost identical to Coke, and they keep dialing that recipe in (and make it retain carbonation better), I think combined with recent health fads (even you, MAHA), there is really no downside to pushing Coke Zero over regular Coke.
Date: I think this will happen within the next 5-10 years? The rebrand of Coke Zero from black can to red can/black text seems to have really moved the needle on its popularity - the train is moving quickly. If there is any company that can nail the turnaround of something this, it is modern-day Coca-Cola.