Pantheons bound to go all in on that shite, no way on earth they'll limit it to xp pots and harmless stuff. They've already said that the game will have transmogging and the ability to rename items.
Don't you get stat items and extra bag space and stuff already for pledging the higher tiers.
Yep. Although Michael "Artois" Butler says they're all cosmetic, while in the same
thread, confirming they are in-game items that
increase your carrying capacity and/or go into equipment slots.
Wrap your head around that logical fallacy, and you'll be Nirgon's new best friend.

They have never, nor will they, until launch I suspect, ever actually state what advantages or rewards the pledge items provide, in-game. It would cause too much negative reaction and reduce pledges. To get the buy-in from the whales, they had to promise the entire ocean. Difficult to follow through on promises like that.
They've always said a cash-shop would likely be a thing, and there's not a snowballs chance in hell they're going to stop at cosmetics. No-one ever does.
They'll remove the entire original team, if necessary, to implement Krono and XP Pots. All in pursuit of that sweet sweet green.