"We decide, based on our understanding of the game’s history and audience, what artwork or lore to pull forward, what artwork or lore needs to change, and what artwork or lore should be buried so deep that it never again sees the light of day. We have a couple guiding principles:"
" - If the artwork holds up or the lore has been true in every past edition of the game, we think twice about changing it.
" - If the artwork or lore hasn’t withstood the test of time, we can update or discard it."
"The number of eyes on a stock beholder has been consistent throughout D&D’s history. No need to meddle with perfection, I say. On the other hand, if you’re familiar with old maps of Waterdeep, you might recall that one of its seedier avenues was named Slut Street. When we updated the map for Waterdeep: Dragon Heist, we gave that street a new name. The old name was never good to begin with and does not withstand the test of time."
In this D&D Studio Blog, Chris Perkins describes the D&D Studio's position on canonicity.
dnd.wizards.com