Considering that the 'The Darkening of Tristram' event is planned as an annual event to run through January I would think so. Perhaps even earlier to avoid releasing a major patch on the running up to/aftermath of Christmas.
It would be somewhat silly to announce it with great fanfare, include it in the current PTR then release 2.4.3 later than January leaving the event to be experienced in the live servers in 2018.
When they cut season 7 short, it pretty much confirmed they were going to cut season 8 short. When you look at them saying they want to have the anniversary event live beginning of January, these dates all line up.
I really cannot wait to get some information on this new cube recipe.
They said they have a ton of ideas, scrapped most, but are looking to implement a few. So this could be remnants of a failed attempt, or something revolutionary to the game.
The word infusion would lead me to believe that you can put legendary powers of one item on ANY ITEM OF YOUR CHOOSING. I would think this means they will make the power unique to equip, so you cannot stack one insane buff.
That being said, being able to infuse a legendary power onto a pair of shoulders that just is not quite helpful for you build would be amazing! It can really open up some unique gearing options.