So beyond just being a "when will this be a thing" thread this is also kind of a "process of elimination"/"what we know" type of deal.
This motif was datamined a while back, as well as a picture of a style material (which I can only assume will be "Etched Molybdenum" given that it's the molybdenum stone with a Breton icon carved into it), and this hearkens all the way back to the Greymoor era, alongside Ancestral Akaaviri, Nighthollow, Wayward Guardian, Ancestral Reach, and Arkthzand Armory.
Furthermore, of those motifs, we have 92 (Ancestral Akaviri), 94 (Ancestral Reach), 95 (Nighthollow), 96 (Arkthzand Armory), and 97 (Wayward Guardian). Given the absence of a Motif 93, as well as its numeric position between two other Ancestral motifs, it would only make sense that Ancestral Breton is our missing #93. Thus, it's not likely to be a style page or such.
As for obtainability, here is where we hit a snag. Since thus far all ancestral motifs have been antiquity leads that drop from treasure maps, it would only make sense for that trend to continue. Granted, that may not mean a thing. the base game zones are already taken with Ancestral Nord/Orc/High Elf, Greymoor's already taken with Ancestral Reach, and now Blackwood with Ancestral Akaviri, and putting Breton in a place like Vvardenfell, Summerset, or Elsweyr seems unlikely. Craglorn could maybe be one, or Coldharbour due to the motif's association with the Ravenwatch Vampires. Maybe Orsinium for the irony that Ancestral Orc is found predominantly in High Rock and Ancestral Breton is found in Wrothgar, but I dunno.
TLDR—we ever gonna actually get this motif, ZOS? there's a hole in my motif-dex and it's starting to annoy my OCD.
Shortly after the formation of the Ebonheart Pact, a Nord woman was given a tour of the Tribunal Temple. When later asked about the experience, she seemed upset. Suffice to say, the Dunmer were not pleased to hear this, and thus they inquired further.
"Well," the Nord frowned, "the priests were very angry and unwelcoming. They kept shouting things at me like "you can't drink that mead in here!" and "somebody stop her, she's running naked!" and "we can't catch her; she's covered in grease!""