I popped a support ticket, here's hoping they answer it. C:

yep same bug here mby we will get it later

i tried and nothing is there

It is empty for me, might have something to do with steam idunno

No, you don't have to do that since there's nothing there if you claimed the box already before today.

im not on steam and still nothing 

I have claimed the package from the Web Storage, but still no outfit. I only received Classic Outfit Box.

I also don't have anything other than a GM letter in my mail and there's absolutely no instructions on how we're supposed to claim any of these items either. I figured they'd just be mailed to us when I paid for it.

Editing to update that after checking the Web Storage on the account page like another poster suggested is what I needed to do. Check the boxes for of the Eternal Winter things and choose to send them to the region your account is on. I got two boxes and between both of them all of the items are there.

No, it states it should be in our mail after the April 6th maintenance. 

(Apparently that message on steam was wrong. It's now showing up in web storage)

same here got everything except the eternal winter outfit, winter pet and dragons box.  and nothing else in mailbox/web storage