Sakura150612, the Lost Zone returned after having been abandoned just before the Black & White era began, but that is a mechanic that wasn't expressed through a specialized class of card. Oh, Dark Pokémon were introduced in Team Rocket (April 2000), returned six sets later in Neo Destiny (February 2002), then showed up one final time 10 sets in EX - Team Rocket Returns (November 2004). Of course, that still isn't a massive gap, but it sure seemed like it to players at the time.
Anyway, you're right that it was probably just some laziness on the designers' part. All the "Fairy Charm" cards have the exact same effect text except for where the Energy symbols that reference what Pokémon's damage is being blocked and where it mentions Ultra Beasts... which is the same place all the other cards have Energy symbols. When we put two and two together, we get four.
There is one thing that could lead Pokémon-EX to return; a mandate that Mega Evolutions must return. Even that requires the powers-that-be decide it is just easier to handle them "the old way" instead of coming up with something new. Since we have the Restored Pokémon mechanic for the BW and XY sets but the "Evolves Trainer played as an Item" mechanic for the SM-era, I don't think they'll feel all that constrained by older Mega Evolutions floating around Expanded.
If you do not have Private Messages enabled, it really limits you in discussing the Pokémon TCG.