Please let me offer my opinion.
Reasons why the next format will be FRLG-on:
- FRLG reprinted Life Herb, a card that had just been printed in the set before it, HL. Have they ever done this for no reason what so ever?
- FRLG has the starting evolutions in it (i.e. Blastoise, Charizard, Venusaur). There has never been a base set that hasn't had one pair of the starting evolutions in it. This might not apply to before Neo-On though.
- Many of the cards in HL are being reprinted, maybe not with the same attacks and stuff, in the newest Japanese set. These include Walrein, Machamp, Gorebyss, Huntail, Lanturn, and Shiftry. To some, this might look like the perfect chance to combine the new with the old, but seriously, would they reprint these pokemon if the old ones were not being rotated out? It's not one pokemon, it's 6.
- The japanese format currently is FRLG-on (only in japanese set terms lol).
- FRLG has a larger variety of supporters, trainers, and special energy. HL was mostly stadiums and tools. There was a total of one supporter in the whole set and no special energy at all. Base sets aren't built like that.
Need I go on?