Today is the day of the Tasha's Cauldron of Everything release. Answers quoting its content starting showing up yesterday. Since it is here now, obviously this question does not apply to Tasha's anymore. But the principle still needs to be discussed so it can be put into practice in the future.
Should we refrain from posting answers that rely on quotes from unreleased content?
Some points to consider:
The community at large would not yet have access to unreleased content, so the typical community moderation cannot be done - quotes cannot be verified for accuracy.
Being able to quote unreleased content is very suspicious. It seems likely such access is gained either through piracy (leaks) or the violation of an NDA, something we are vehemently opposed to.