It’s been mentioned multiple times in different dev posts. They’ve also said a few times it’s going to affect very small percentage of avatars, and that any avatars that do go past the limit can absolutely be easily cut down. Just make sure to not have all your textures set to 4k, masks and normal maps you can easily go down to 1k or even lower without quality loss.
It’s not that they haven’t been telling people, it’s that people aren’t reading the dev blogs. 