re: Predictions from the Apollo era were that those footprints would last for at least a million years
There are things we now know about the Lunar surface we didn't know when scientist made statements about a billion years duration for footprints.
First, is micro-meteorite gardening which is process where the near surface of the Moon is cycled under thus the name. It's like someone taking a spade to the surface and turning it over. The question is how long this process takes.
Second, Moon Storms a little dust storm that follow the terminator. So they happen every sunrise and sunset on the Moon.
These surface disturbances/weathering probably would take sometime to remove the footprints. So maybe I'm exaggerating to say the footprints are gone, but for sure they won't last for billions of years.