The core of my argument was against "There is no reason to think that LLMs will improve at all." This is a falsifiable statement if there is one or more reasons to think that LLMs will improve. I provided one such reason. I don't disagree with the part of the statement that "They may degrade to due lack of clean training data." as instances of this have already, and will in future happen. However this is immaterial to the totality of the statement.

Your argument is that there are some reasons to agree with the statement. To show that my argument is false you actually need to show that there are no reasons to disagree with the statement. In effect you're attempting to argue that because you saw some red cars means that another person's statement that all cars are red is true.

Meta argument aside, there are many other reasons to suggest that LLMs will continue to improve, the easiest of which is they have done so recently so far.