Koei Tecmo just opened a new teaser website for a new game that will be announced next Monday, which is the time of the biggest E3 conferences.
The teaser mentions that the game is by Omega Force, matching a previous tease, but reveals one more detail. The message in Japanese translates as “Of “Musou’s” History, the most evil.”
Interestingly, this could also be a play-on-words, because “most evil” or “most vicious” (saikyo) reads the same way as “ultimate” even if the second kanji is different. Japanese developers and publishers love this kind of wordplay where secondary meanings are often implied due to how words read.
Your guess is as good as mine as what it could be, but the color scheme is definitely ominous.