Although we have already had 1TB hard drives included on an Xbox One console before, that was as part of a bundle with a game- if you want to get the system standalone, you don’t have much say in the matter, it has to be 500GB or bust.
That may be about to change soon, as it appears that a Spanish retailer, Lamee Software, has apparently put on its website an SKU of the Xbox One with 1TB of on board storage. Notably, this system does not come bundled with Kinect.
The bundle will be priced 449.99 Euros, and apparently will launch June 23, which means that it is ripe for an E3 announcement. I would say to take this with a pinch of salt, but really, this seems very likely to me, and I am pretty positive that we will be seeing a 1TB model of the console going up for sale soon.