Lysandre Prism further strengthens my theory that the Lost Zone will be important soon. I also dig the art on it.
The Lysandre sleeves look cool, too.
The [Prism Star] mechanic makes it important. Period. I fear you are correct because I am worried that the powers-that-be will forget/miss the point of things like the Lost Zone (or Removed From Play area, Removed From Game area, etc.). We've had various one-per-deck cards before, and of the two things that usually "break" them, one is that sooner or later we have a way of reclaiming them from the discard pile to reuse what was intended as a once-per-game effect. Right now, sending the [Prism Star] cards to the Lost Zone is as close as we can come.
Then again, I thought the same thing of the GX-counter for GX-attacks, and we just got an exception to that in the cards revealed as well. Then again, it is a Pokémon (and thus so far a GX-attack) specific option, so it could still prove well balanced.