Let's say certain things go right and they experience a population boom, around the time of the first Adyghe kingdom ca. 400 BCE... One group of Adyghe/Circassians then moves out of the North Caucasus and onto the Pontic Steppe (the ethnogenesis of the Proto-Indo-Europeans may very well have happened this way, if *PIE influence on/from Kartvelian is any indication); there they adopt a nomadic lifestyle under the influence of Scythians, Sarmatians, or Alans - whichever Iranians are most prominent at the time - and end up folded into one of the hordes invading Rome (assuming Rome still rises).
Bam. *Circassian horse-lords in Pannonia, Transylvania, maybe even the Balkans or Central Asia.