The numbering is interesting. Based on the info we know every Pokémon will get a AR or SAR, Serperior ex sar is 169, while reshiram and zekrom are both 174. I assume at least 6 ex's per set so probably it's like 173 is the sar of them both, and 174 the bwr. So 175 should be a ex sar, or am I...
What I think is, that they really planned something gen 5 related but scrapped it for unknown reasons. The go events, this set, khus hints etc. But I doubt there will be a new gen 5 gamę.But I'm Here for some gen 5 love in the tcg