koala no interest is already expanded enough, we’ve got brawls in costco now, don’t give them any more ideas 
Jokes aside, popular Pokemon sets are only interesting so long as they’re unique. Each generation’s second or third set has been a Charizard set since XY. Now they’re kind of boring. Who wants Darkness Ablaze or Obsidian Flames? Even Flashfire has been stagnant in price. Hidden Fates and Shining Fates were the greatest sets ever until people realized we now get a “Fates” set every generation and they’re also kinda boring when compared to the special arts.
Eeeveelution and Pikachu sets are cool, but if we keep getting a special art Eeveelution set every generation then I think they will quickly start getting less interesting and people will shift to whatever new gimmick Pokemon has. Maybe they go back to gold stars or Trainer’s Pokemon get hot. Either way, I don’t think Pokemon will have any trouble with cultivating interest. In fact, it’s likely in their best interest to not keep going back to the popular Pokemon well and instead branch out with new ideas.