Although not very original and it bucks their naming trend thus far, I would got with Xbox 4. I think it will be important for them to be clear with the name and avoid getting too cute. However, I doubt they go with Xbox 4 because Playstation will no doubt keep their number designation which of course will be "5". The marketing department will see that as a negative and convince the powers that be it is a poor choice. So, realistically I expect them to use some sort of name. I could see them using "Infinity" for example.

It will be called either Xbox Two, or Xbox 10, referencing the newest OS from Microsoft, Windows 10.

Xbox Minus 358

It will be called windows tv

I believe Microsoft skipped Windows 9 because they must have had an operating system that was closely associated with Windows 8.  Considering that Windows 8 was a huge flop, they must have scrapped Windows 9 and the name as well.  

How on Earth would Microsoft be able to skip a name in the console business and name their next console "Xbox 5"?  They would be laughed at and ridiculed to no end.  

After all the issues Xbox one had, launching as a multimedia device instead of a gameing focused consol....

I just dont see MS doing that :P

Mr_No's; suggestion of Xbox 10 (because of windows 10) is the most valid name, apart from Xbox Two this thread has seen, IMO.

I like Xbox 10 as well.

Xbox, New Xbox, or Xbox 10 is my guess. Better not be something stupid like Xbox One+.

Xbox 2

Xbox Live.