Starting on May 10th you’ll only need one copy of any given card style to be able to use it across a playset in a deck.
For example, if you have one copy of the Strixhaven Mystical Archive printing of Opt you’ll now be able to choose that for all four copies that are in your Izzet Prowess deck, so long as you own any other 3 copies of the card. Previously, you would have had to open or craft four separate copies of just the Mystical Archive printing. Now it doesn’t matter how many of any one specific printing you own, so long as you own enough across all printing to put into whatever deck you’re building.
Additionally, if you already own 4 copies of Opt and a new version is printing in an upcoming set, once you have a single copy of the new printing Arena will treat that as if you have 4 copies of that printing, making it easier to complete full collections of new sets.
The above also applies to Art styles, in that previously you would have needed to own the base version of a card to apply that art style. The example given in the article was the Mina Harker version of Thalia, Guardian of Thraben. Under the old system you could only apply this art style to specifically the VOW version of Thalia, but starting on May 10th you’ll be able to apply the Mina Harker style to *any* copy of Thalia, Guardian of Thraben regardless of if it’s from VOW, MUL, or any other set in the future.
Maybe the biggest change coming on May 10th is that you will now be able to craft any printing of at whatever the lowest rarity it appears on Arena. Goreclaw, Terror of Qal Sisma was originally put on Arena as a Rare in Core Set 2019, but as of Pioneer Masters there is also an Uncommon version of the card on the client. Starting with this update you’ll only need to use an Uncommon wildcard to craft any version of this card, including the Core printing that was at Rare.
As part of this change any preconstructed decks bought in the Arena store will now discount your purchase regardless of which printing of a card you already own. Currently, the discount only applies if you own the exact version of the card in the precon.