No doubt they're taking their sweet time with it. Then again, knowing the Mastodon user base, whenever it is implemented people will probably go crazy and think it's the biggest invasion of privacy since the gestapo.

By the way, here's from Monday's development update:

The team also made significant progress on the specification for Quote Posts. It needs a few minor changes, but we expect to publish it for comment in February, and start implementation right away. The current plan is to publish Mastodon 4.4 with support for displaying Quote Posts, and then add authoring in Mastodon 4.5.