Well, if you accept Irn-Bru as a Cola replacement then Germany already isn't a Cola country anymore. The vast majority of sodas consumed is rather of the Cola-Mix kind (there are two very common products named "Spezi" and a ton of smaller brands) and Apfelschorle. CocaCola dominates the Cola market only, the sum of all the other sodas is far greater.
I am from germany and this is true. I can remember the 90s and 2000s where coca cola was totally dominant and the only thing you can get in bistros restaurants etc. but now only cheap places like döners serve coca cola. what I meant is that they are still one of the most sold brands in western europe but not as dominant as it was with a steady decline. While in other parts of the world they can sell their sugarwater without regulation and thats where they make money. the rest of the world wants a taste of the free world drink.
That's a really good source (albeit from 2017), but while it does support your argument that sales by other companies dwarf those by Coca-Cola, the latter is still firmly in first place, with 3.3 billion liters sold -- as much as the companies placed 2 to 4 combined.
I guess Coca-Cola will not be replaced in the top position in any short to medium timeframe. While they will dwindle, I don't think one big competitor will gather their market share, rather a lot of small ones.
