The second announcement that Arc System Works made at EVO 2017 was an entirely new game, titled BlazBlue Cross Tag Battle. As the title suggests, the game is a 2 on 2 tag team fighting game. Also as the title suggests, it features not only BlazBlue characters, but guests as well, from Persona 4 Arena, Under Night In-Birth Exe:Late[st], and RWBY.
You can see the trailer for the game below:
The trailer shows off the tag team combat system, as well as assist supers. It also shows five playable characters: Ragna the Bloodedge and Jin Kisaragi from BlazBlue, the protagonist/Yu Narukami from Persona 4, Hyde Kido from Under Night In-Birth, and Ruby Rose from RWBY.
No announcements were made regarding release platforms, but we know that the game will be coming sometime in 2018.
Arc System WorksBlazblueBlazBlue Cross Tag BattleEVO 2017Persona 4Persona 4 ArenaRWBYUnder Night In-Birth Exe:Late[st]