it's like you all get amnesia or suffer some mental issue that makes you think, despite all experience to the contrary, that THIS TIME some magic will happen. Last time it was "They could announce at Gamescom!!!" and despite all of the logic against that, you refused to believe if. Well, BfA isn't going to arrive significantly earlier either.
Beta to release is about 5 months on average. They're not starting beta earlier than Feb. That would put a release in July. Even if they DID start beta in, say, the last week of January it's effectively the same thing. Legion released at the end of August 2016 so that would be 23 months... dead on average for most expansions.
Let's say that beta starts in mid January and lasts 4 months... that's May, again about where you'd expect it to be based on average expansion live (20-23 months).
Or let's say beta starts in April and again is about 5 months.... that's September. Getting a bit long but not terrible and 24-25 months.
That's your range. May-Sept. It's very unlikely to be much later than that or much earlier, no matter what you all might wish.
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They've release content on the same pace as they did in TBC, LK etc. One complete cycle every 5 months. All they did... ALL they did was play mind games and break the raid and non-raid content apart. I think that's brilliant because there are a lot of people like you who feel like you got stuff faster when you didn't get more content faster, you just got the typical content but delivered in bits so they could give it to you more frequently. Same amount of content and thus work for them, but the players get something every 2.5 months vs a big drop of stuff but every 5 months.