KoF XIII was first discovered on Steam's database in February along with several other games like Dyad and Fez, some of which have now released on the service. Entries for KoF 2002: Unlimited Match and KoF 1998: Ultimate Match were also unearthed back then, but the KoF XIII trailer provides solid indication that particular game is headed to Steam in the near future. No official announcement has been made.
SNK Playmore's latest entry in its almost 20-year-old fighter series arrived in Japan's arcades in 2010 before coming to Xbox 360 and PS3 a year later. Joystiq's resident King of Fighters, Jordan Mallory, doled out four stars in his review, deeming it "hands down the best, most polished and solidly constructed King of Fighters game there's ever been."
Update: The trailer has since been removed from Steam. You can view a copy uploaded to YouTube (via Shoryuken) here.