It means they will most likely save any kind of 8.3 ptr build for after Blizzcon. Means 8.3 will be discussed about at Blizzcon, and most likely just a little bit about the next expansion.
They are starting to take their time now with the upcoming information they have planned for WoW and its future seems like.
The Virtual Ticket stuff coming in October (based on the Twitter comment) also means the VT probably has hints to incoming expac/end of BfA. I don't recall not knowing the VT goodies that close to a Blizzcon before (but possibly they could've) - - - after some quick fact-checking it seems Blizzcon 2017 virtual goodies were revealed October 10th 2017.
https://wow.gamepedia.com/Virtual_Ticket
These VT goodies included the flying mounts for Horde/Alliance meaning it coincided with the next expansion.
That means the VT goodies coming for this Blizzcon can also give way to what's going to be in the next expansion and probably why it's another "late" VT reveal.
They're really pulling all the stops from my view to ensure the ending of BfA and start of 9.0 is kept as mum as possible. Dunno why, very strange, but interesting on another hand as well.
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Looks pretty green to me from official artwork from Chronicles. Although he's been shown as Black/Red/Yellow/Orange too.