Were they forever replaced by Z Stones or will they return at some point?
Nah, they're gone. Not really sure why you'd want those stones over z crystals anyways except for unburden and acrobatics
>>32160661
Z-Moves are more powerful than Gem-boosted moves, and non-damaging moves can also be ugpraded, so the Gems are redundant now
>>32160671
They look nice.
>>32160671
Well, after use the item slot is free again
Also your 1 z move isn't used up
i like to believe that they sidelined them forever once they made gale wings
>>32160677
Gems definitely do leave open some nice item-swapping shenanigans.