in a previous chapter when Tanjiro faced the hands demon, he said they are in the Taisho era which was between 1912 and 1926, there's already western clothes and technology here, and considering KnY first debuted in 2016, I assume the next chapter will probably take place after such a long period of time, likely in the 2000's, we will get to see our characters as old people mostly, maybe even witness some deaths from old age or the curse. Or, and this is a bit of speculation, the author will try and tie up the Academy tales AU with the main story somehow.
From my understanding though, the academy AU already have some sort of a light novel with chapters, I only found two chapters online but I don't know if there's more, they're official, considering there's art of the characters with the author's style on them.