Wandering around PJRC website, there are a few pages which would need updating.
I know Paul is so much busy, but at least let's keep track:

Pictures: Teensies 4.x are missing
"Key features" table: even 3.2, 3.5 and 3.6 are missing
I would also remove references to 3.1

Missing 4.x
Title is wrong: "Teensy LC (Low Cost)"

"Hardware" tree-menu on the left column misses 3.5, 3.6, 4.x