The important part isn’t the new merch. I mean sure they want that to sell. But there’s a reason why live Snow White wears the same blue and yellow dress as animated Snow White. It’s a sneaky way of renewing the copyright on that look. So now that look goes from hitting the public domain in 5 years (meaning anybody could make and sell Snow White merch) to some time next century. 6 months from now nobody will care about or remember this remake, but 6 years from now when Lego wants to make a new set of Snow White stuff this remake will matter a lot.
No, it doesn’t work that way exactly. The animated version will lose copyright status and anything with that exact look will be fair game. The new version with the less liked person will be in copyright but no one cares for that.
Disney can still sell old merc after the copyright ends but so can anybody else.
Mickey Mouse is in the public domain now, but only the old original version. In a few years, other versions will join him. Disny has run out of ways to extend public domain and no one will help them this time.