It's a tiny ball, mind you, and not remotely a big deal, but when you're performing on the level that Wizards is, you're playing a game of inches
If Koya leaves the battlefield before the delayed triggered ability goes on the stack at the beginning of the next end step, the delayed triggered ability will still resolve as normal
Its unlikely well see a better variant of the card since Ponder and Preordain are currently banned in Modern, so it would be a surprise to see a similar card at a lower mana value
Even if you are fortunate enough to have one of the packages hit a charizard, that $375 has near fully wiped out expected ROI since the value of the card ($1000) - cost of the pack ($500) - cost of scanning packs ($375) - cost of grading ($40-100) leaves you at best a 10ish % profit on this one pack, but the other 4 packs have now been confirmed duds and either need to be sold to recoup value (most likely breaking even at best), or put away to be sold in the future
"The Changing Tap Symbol"