The culture didn't shift much post-Sourcefire, it just melded a bit. Everything they acquire becomes a little Cisco-y, depending on how big it was. Duo will become "Cisco-y Duo". But it may be more Cisco or Duo depending on the strength of the culture.

Talos is a good example: it was created from merging Cisco SIO and SourceFire VRT, but I would wager it's 80% VRT [in terms of culture]. They also have so many researchers now that it probably has sub-cultures. Even a single remote office can have its own culture.