BlizzCon 2021 is nearly here, so people are likely to start shuffling into their streaming platform of choice soon. Due to the situation with the pandemic, things look a tad different this year. This time around, the show is entirely online, and as such is called BlizzConline – I know, it's a lot, but it's fine.
You've got your choice of Hearthstone. There's also a StarCraft 2 tournament for funsies.
As for what Blizzard is revealing, we'll have to wait and see. The studio accidentally leaked World of Warcraft: Shadowlands next update by releasing the press releases early – whoops. That said, there's likely some new details to be gleaned from the show itself – so we may get more specific release dates than the ones given.
There are a few ways you can watch the show, but one of them is below:

There's still some time to go, so you can peruse everything we know about Diablo 4 if you fancy it. You can also find the official BlizzCon 2021 schedule right here if you need it.