According to sources its for 360 not Xbox One & I would likely expect a PC release too, im guessing its being used as a stop gap between Fable III & Fable IV.
The HD update will feature new Achievements, leaderboards and full 1080p visuals with lighting and animation powered by Unreal Engine 3. The HD version will also include all content from its expansion, Lost Chapters, and utilise an updated save system.
Quote from Ted Timmins: It's the game that the Fable fans have been demanding from us for years now. Our art director has been working really hard to bring the game up to 360 quality levels that people expect... we're actually using Unreal 3 to render all the lighting. Then we've got a new facial animation system and new cut-scene animations, so all of the cut-scenes look absolutely incredible now - they're much more up to what you expect from modern day standards. We've been looking at the textures, the models, the meshes, the particle effects... the whole thing has been redone.
I played through the original Fable several times to pick out the things that I "didn't like the most." That included the "outdated" UI, "very long" loading times and the control scheme which was subsequently "vastly improved" in Fable 2 and 3.
Lionhead are also planning to add content to Fable Anniversary, starting with SmartGlass functionality.
Ted: I'm one of these people who always has multiple gadgets on the go and is always distracted. So it was really [about] how we could take that distraction and turn it in to something that... I'm playing the game and I have this really cool companion in my lap or hand that's actually in sync. It's my map and we're actually looking at having the ability to take screenshots from it that you can share with your friends... it's really about making it something that you almost don't know is there, it's like it's almost part of the same thing. We definitely want to investigate entirely new Fable expansions and I've certainly got a whole bunch of ideas that I'd like to realise in the form of additional content.