Not a horse-tux, sadly. Nor is the cheesy avatar of an open source operating system becoming a playable MGS character. Big Boss gets the tux, D-horse gets armour, and playable women soldiers get [sigh]. This, then, is the first DLC for the mostly excellent Metal Gear Solid V: The Phantom Pain [official site].
No price or release date as yet, but a reveal during the Tokyo Game Shame gave us our first look at this costume-centric add-on. Snake/Big Boss gets a couple of outfits recreated from MGS 3, but the star is surely the Bond-style tux, which very much makes our one-eyed beefcake adopt the 'gorilla in a suit' look. This outfit is often an MGS end-game reward, so bit a (potentially controversial) break with tradition here.
D-Horse, meanwhile, gets one set of armour which looks a bit Roman and another which makes it look like he/she is attending a royal parade. Clearly, Horse Armour is DLC's least finest hour, but in this case I'm prepared to be more generous - MGSV's least-interesting buddy could do with a bit more silliness if we're to ever take him with us instead of D-Dog or Quiet again.
Speaking of exploitatively-presented characters, if you're in the habit of making a female solider your avatar, this pack will bring two lady-centric costumes, styled after The Boss and Eva from MGS 3. They involve boobies, because Kojima. Very disappointing that, at the very least, this DLC didn't include practical military clothing in addition to the pandering stuff. The Boss's costume (left) is even zipped up for the vast majority of MGS3, so it's not exactly maximum authenticity anyway.
I say 'because Kojima', but truth be told it's unlikely he's involved with MGSV's post-release content, given his apparent departure from the series and Konami after their latest round of public spats. This may well mean we never see any story or mission DLC for the game, which is a great shame.
You can see the full TGS MGSV panel here, though it's all in Japanese: