Not sure where the stream is, but I’d guess it’s at Microsoft’s Twitch page located here:
You can also watch it live on your Xbox One with the Xbox Live Events app.
Get hype!
EDIT: If I’m not mistaken, the announcement is something called the “KI Ultra Tour”, which I’m gonna guess is similar to Capcom’s Pro Tour. 100k is on the line, and more info on it will be available later this Summer! It connects with the KI World Cup in some way, too.