Did some quick math to see a ballpark estimate of how many cards a master set would hold and it's going to be at least 418 cards.
This is guessing that there's only going to be 3 full art supporters and 3 secret rare items from Explosive Impact, which is most likely wrong but I was just basing it off other sets.
There's also going to be alternate art cards and possibly alternate foils so that would make the master set increase even more so in size.
It's pretty insane honestly, master sets of something like Aquapolis or even Boundaries Crossed were already crazy enough, so this monster is going to be something else.