I have the files for The Preppy Lion books in a folder on my hard drive that’s gone through moves from who knows how many computers since around 1990ish and I found a letter to an editor at Springer-Verlag from November 1992 with this gem of a sentence:
Because LATEX 3 is likely to appear in approximately two years, the latter volumes are currently at a low priority.
Also, loads of old stuff for volumes 2, 3 and 5 that I’d forgotten about.