Alright, so the ANN thread is dead, the website looks abandoned too and 2009 style.
I recieve no slack invitation on any email provider. So... either buterin has some great inside knowledge or is fucking trolling which seems much more likely.
It is definitely alive and in the middle of changing to a new name, they do not spend much time on here at all as their old ANN became a playground, most stuff is via their slack.
The tweet is no doub being sarcastic but has helped with exposure, it really is a coin to keep your eye on, I am looking forward to the next few months when they release their platform.
more info on slack
https://dls2.typeform.com/to/FlV309They invite manually so it might take a bit of time.