I expect quite a few more teams to participate in this week's. Last week's tournament was notably missing EnVyUs.
Apparently ruwin left mixup team - it'll be interesting to see who they'll pick up for the spot. Wonder if it'll be someone from tf2 (indust?) or someone else from the OW scene. Regardless looking forward to seeing some good games!
Edit: Also prize pool doubled apparently http://www.gosugamers.net/overwatch/news/34380-gosugamers-overwatch-weekly-prize-pool-doubles
He wanted to play a DPS role but there wasn't a spot for that on the team as well as some other issues he hinted at.
It looks like Mix^ has picked up TviQ at least for this week though: http://www.gosugamers.net/overwatch/teams/14586-mixup