Arena teams are now gone from the UI, allowing you to group with whoever you want, similar to the rated battleground system. This will also come with region wide matchmaking, allowing you to be matched with anyone in your region, not just your battlegroup. There will be a blog post that fully explains the changes on Monday.
What is your opinion on this?
I always wanted the option to join more then one team but this doesn't seem to fix that, you can in fact play with whoever you want now.
But you still have a rating across all teams, so I can't go and play with my 1600 IRL friends with 2100 CR, because assuming it works like teams, a loss would be huge.