On the SG Xbox One dashboard, there's a link to "Pre-Order Hitman Today". Clicking it leads to the store, but no option to pre-order. The usual button with the price information is replaced with a "Visit Game Hub" button that leads to, well, the game's hub, without any purchase option. I guess just have to wait a few more days - it was the same when Assassin's Creed Chronicles: Russia was previously on "pre-order".
There'll be no disc version of this game until next year since it's episodic. The special edition box set is also ridiculously priced (over $200) if you intend to import it. Fancy paying over the odds for a download code (ok, it comes with some goodies).
I can't wait to play this game, so at the moment it's a painful wait.