Tsunekazu Ishihara has released additional details about the games. Among them is the following tidbit:
What could this be in reference to? We got a stat overhaul in Generation III, but technically that doesn't count as a battle structure (only an underlying one), nor did it make Pokémon stronger, but rather more diversified. We also know from Masuda that Game Freak don't intend to cut backwards compatibility, IVs or EVs anytime soon (he said as much when he was asked about those things in a Q&A session last month).The bonds between players and Pokémon will deepen, and Pokémon will become stronger with the new battle structure.