Goo'boy.
Seems your question is chasing it's own tail (my srcasm/general humor facilities are still asleep) -- why indeed would we need speculation threads when we already know the release date?

We might revise that particular "rule", but there's really no need for any speculation of that kind now any more than it was before we knew. Feel free to discuss in threads about the release date.
This is off-topic, and now cleared up, so *click*.
(feel free also to point more questions about rules to the moderation team)