While we had a pretty good idea that El Town was joining the 343 Pro Team, it is now official. From the latest Community Update on Waypoint:

We’ve got another member of the Halo Pro Team here at 343 Industries! Professional Halo player Visal “El Town” Mohanan has joined the team to help us with Halo Infinite. He is known for competing in multiple Halo titles and placing second at the first Halo World Championship in 2016 with Team Allegiance. His unique playstyle and ability to create new metas in the competitive scene will be a great asset to the team here at 343. Please join me in welcoming him to the studio!

We are liking how the Pro Team is shaping up. The roster as of now is Clutch (Team Lead), Heinz, Mikwen, Gregor, and El Town.