You'd still be going backwards. Classic Link is an already existing design who just happened to appear because Nintendo wanted to cash in on another nostalgia game. Toon Link is clearly more unique and different from Normal Link than Classic Link is as well as more preffered. It wouldn't be logical to change it to a Link with hardly any uniqueness other than being young, not to mention Toon Link is young, there's really no motivation to replace him if you already have him, it'd be a waste of development time. It'd just be a
muh recency situation. It just doesn't make sense.
It's not a recency issue of relevancy, Noah, but rather moving towards the future by looking back into the past... by having Classic Link replace Toon Link, he would be progressing forward the Zelda series in terms of general representation - AKA showcasing different periods of time for the Zelda series. With the original Triforce (as well as Link representing his game at the time), you almost always have a another Link who represents another aspect of Zelda - Child Link with OoT/MM, Toon Link with WW, and now if we have Classic Link with LttP2, we would follow the cycle. It's only logical.
Replacing the Younger Link isn't much of a pattern. It only happened once and because Toon Link was more unique and made more sense and was the only Young version of Link being used at the time.
OR there IS a pattern that you're not seeing, and are either ignoring altogether or something else... either way, we'll have to wait and see.