Here's what I think: This is our last XY set. Despite being advertised as a concept pack in Japan, the thing is, unlike Premium Champion Pack (which was released 1 month after Awakening Psychic King - our Fates Collide), this is being released in September, following the pattern of Japanese sets being release every three months (Blue Shock/Red Flash were released in September too, for example).
From what I understand from the news post, the set will have secret rares, mimicking regular japanese sets in that way too. While they may be reprints, I doubt they'll be exact reprints like Premium Champion Pack. But I think they are indeed new cards (and hopefully we'll get Mega Pidgeot and Pinsir since this set focus on Gen 1).
So, after this the next japanese set is supposed to be released in December, after Sun & Moon already came out, meaning the next japanese set will most likely be the first Sun&Moon set.
How does this translate to us in the west? Simple, weather this is a set of reprints w/ new artwork or new cards, we need something for our November release so my guess is TPCi will treat this as a regular expansion and make this our last XY set.
Sun & Moon are released in that month but we get our Sun&Moon set in February as usual, with maybe a starter set a bit earlier to bridge the gap, in the same way they did it at the beginning of XY...