Apparently XBox One is going to be an open platform. So you won’t need special permission to write games for it.
Does this mean a future version of Unity might create apps/games for the XBox One?
That would be very nice! 
XBox One support has already been announced.
http://www.gamasutra.com/view/news/199810/
As to what permissions you need on any console platform is up to the platform owner.
In fact isn’t Max: The Curse of Brotherhood (Launch title for Xbox One) made with Unity?
That’s great!
Now to decide whether it would be worth buying an XBox One for £430.
I would need one sale a day for a year of a £2 game, say, to make my money back. I wonder how XBox gamers will respond to these new indie apps… It’s a gamble.
i’m sure ms will still require some kind of activation or license key or always online scheme. if they just let anyone run any code they wanted on it anytime, they would end up with some problems pretty quick.
Well you just look xblig which was a sewer.
Check out this thread regarding Mantle the new AMD low level graphics api, as the XBox and PlayStation will both use AMD chipsets 
Unless I missed something (and I may have because Microsoft keeps changing their stance) XBox One wont be open, at least at first. They will only give licenses to few group of indies with experience shipping games, and they will need a separate SDK.
They plan to slowly expand on that program, and also to eventually make the off-the-shelf XBox One an SDK itself. Until that happens, if developing is the only reason you considering the XBOne, then hold a few monhts until MS actually opens up.
I think the only reason is because it was buried in the games section. Where AAA and Arcade were at the forefront. This has been sated to change. All AAA and Indies will be grouped together, just like mobile.
Starmans right though. Not going to be allowed till most likely sometime mid next year. So if that’s why you want it, wait. Not enough information available. Its a wait and see game right now.
Although I work for Unity I have no insight into our plans for XBone. Your maths assumes that there will be a free add-on. Given our current console products are orders of magnitude more than the products you are familiar with, you might want to factor some Unity XBone license cost into your business plan.