I would assume they would add additional pages to the vault, as it works with your friends list and currently players list.
Another possibility is that they could split the vault into three different vaults. One for inventory items, one for weapons, and one for armor.
EDIT:
Many thanks for all the replies and opinions!
Can we make it to the trending page??
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Edited by ryanhatfield: 3/17/2015 1:33:19 AMYou need to account for all possible exotics, all possible raid weapons / armor (all raids), shaders/ships/mats, and then also account for vendor legendaries and iron banner gear. So basically the more space the better!