As promised, Valve has released the 7.21 balance update, along with the new ranked season. The update also brings four new Dota+ exclusive sets.
The biggest change from the previous ranked season is that the medals now have 7 tiers, instead of 5. Players will be able to get unique emojis based on their tiers. Another change is that players can now see their numerical behavior score in your profile and conduct summaries, allowing them to decide whether or not they want to behave properly in pubs.
As for the balance changes, most of them revolve around slowing down the game a little bit, with various gold changes (melee creeps give less gold, while ranged creeps give more), as well as the xp changes for levels 7-12. Tier 2 and 3 towers, along with melee barracks now have a little more armor.
You can view the rest of the changes here