I've been reading through the equipment and items chapters of 5e, and I still can't find ruling on wardrobes.
The 5e Wardrobe was split between the Portable Hole and the Chest. The magical Portable Hole holds at least as much as a Wardrobe, while the Chest (though only 12 cu ft) is non-magical, made of wood and and can be placed upright on one end so that its lid becomes like a Wardrobe's door (indeed, it can serve as a Wardrobe for gnomes and halflings).
That's all the Wardrobe you need to play D&D.
A Wardrobe would essentially be a Chest that holds as much as a Portable Hole, without magic, and that would be both absurd and game-breaking.
I feel like the devs have really dropped the ball as far as furniture goes in the current edition.
You can use Mimic stats for any furniture you may need in your campaign. Just don't have them attack. D&D has never had any other furniture rules, and always supported the simulationist idea that all furniture can be 100% Mimic in the in-game fiction. Forcing alternate definitions on us by publishing a Wardrobe entry would undermine the continuity of many campaigns, and drive people away from the game.
Would you like the wardrobe being added to 5e in future supplements? Even a UE article would be fine.
An Unearthed Equipment article would be cool, yes, but you shouldn't expect anything more than a sub-set of the Chest - maybe a 'Steamer' chest that's expected to be set upright and has mechanics for little drawers, for instance. Chests are an established part of D&D tradition, one of the 'big 4' along with 10'-Poles, 50' Ropes, and, of course, the indispensable Door.
Like an actual wardrobe that holds clothing and coats, or a mystical kind that is actually a gateway to another realm?
The pro-Wardrobe 'camp' would insist that the whole point of having equipment like the Wardrobe is to provide non-magical/non-mobile alternatives to storage-role gear like Portable Holes and Handy Haversacks for campaigns that are not focused on exploration but centered around a locality like a mansion, castle, or the like based on the popularity of Downton Abbey or something. Of course, AD&D had rules for fortifications, which are all the castle rules you're ever going to need, and could be easily ported into 5e, but they didn't include and don't need, non-mimic furniture.
But, clearly a magical gateway to another world is a much more reasonable thing to have in D&D than a non-magical Portable Hole or non-Mimic furniture.