YouTube feature on their titles' AI. Both the Warden and Warlord classes were seen fighting in what looks to be a Roman arena, which may also further confirm the Centurion DLC class.
Unfortunately, we were unable to catch a clear frame of the YouTube video to see what the For Honor developers were working on or their file names.
Though the coliseum map could be seen as a dev-only test map to gather data on character changes, the map looks too fleshed out for only that purpose. Ubisoft has plenty of maps at their disposal already and the map shown in the video is not just a floor with bare, surrounding walls. The map has various levels, doors, and design. Just by looking at it, the devs added "life" to the coliseum map with the various architectures and design choices.
At the moment, we've yet to receive any details past the leaked images of the Centurion from Ubisoft, though we have seen some of the skills they'll possess. Most of the Centurion skills are similar to other Vanguard classes, though they have a couple unique ability icons not yet in For Honor.
Depending on how the developers want to release their DLC characters, we may only see the Centurion when the coliseum map is released, or we may see the Ninja and Highlander classes released together with it.
As Season One of the Faction War comes to a close, Ubisoft could release further details about their upcoming content drops including the DLC characters and Ranked game modes. For now, we have For Honor Update 1.06 releasing on PC tomorrow, April 25, with consoles getting the patch likely one week later.