I've also asked this, I think the answer is November 16th. Unfortunately I don't have a good source for this, mostly just posts on the site like these:

https://steemit.com/steemit/@elyaque/daily-steem-report-november-8th-steem-7-19

https://steemit.com/steemit/@mindhunter/2-steemit-random-questions-what-is-your-steemit-resteem-rate-and-why-is-original-content-declining-on-steemit

And my understanding is that the power down time will indeed change to 3 months.