I'm thinking they're new costumes. So far, when it comes to how many "new costumes" they are announcing for DLC packs, they have only counted the new costumes and not palette swaps. Otherwise they'd have been advertising something like 10 new costumes per pack.
8thark, are you British?
I've found the best chance for 8-slot weapons with high rank come from not just the potions, but also doing Network Link battles since they have higher rewards.
Personally, once they're done with the Hero of Hyrule Pack I'm hoping we'll get a Second Wave announcement.
That Boss Challenge mode is gonna make +Beast and +Finishing Blow reaaaaally popular.