A couple of weeks ago, SteamDB leaked the existence of Streets of Rage 4’s first DLC Mr X Nightmare, sparking all sorts of speculation. Today, DotEmu has confirmed that Mr X Nightmare is coming and exactly what it will bring, though the release date. The DLC will add three new playable characters and one of those characters will be Estel, one of the bosses in the base Streets of Rage 4 experience. DotEmu also announced that Streets of Rage 4 has sold 2.5 million copies.
The Mr X Nightmare DLC will also add brand new moves to the characters, and players will be able to customise the move sets of the characters to put together an arsenal of moves. The DLC will also add a survival mode which will add different challenges for players to tackle, though not much detail has been given yet. Along with the paid content in Mr X Nightmare there will also be a free update. The free update will add a New Mania+ difficulty, a training mode, and new colour palettes for the characters.
In our review for Streets of Rage 4, I wrote:

Adrian Burrows
So ready for this. Using a swordfish as a weapon? Yes please!
Klart
Most excellent!