A summary I made up of some of the new information from the video:
The next update is going to be one of the biggest ones ever.
The contracts will have a lot more player choice, players choose the type of contracts they do and the rewards they try to achieve. They call it "Choose your own adventure" internally.
The Pyro class pack will likely have weapons for the pyro that changes the class in some way and has a new gameplay twist.
There will be broad game balancing work, based on comp player feedback. Looking at high level for balance.
It sounds like the Jungle update will be part of the Pyro update.
It will also include community maps and cosmetics.
Competitive will have an ELO system and placement matches.
They're working on a 4-5 minute video for the update similar to the Meet the Team videos.
Valve happened to be working on the Jungle theme update at the same time as the Mayann update.