Whatever it is, it will be really dumb.
• They named the Xbox 360 because they were afraid of people thinking a Playstation 3 was superior to a Xbox 2 just because of the number.
• After painting themselves into that corner, they decided to name the Xbox One (?) because it would be the ONE ENTERTAINMENT BOX TO RULE THEM ALL and TVTVTV and because it would be INPUT ONE on your receiver due to it's amazing TVTVTV integration and they were making TVTVTV shows for it. Oh and it apparently played games too.
So with all this name baggage, the most sensible thing I can think of is to shake that all off, wipe the slate clean and just call it Xbox. Which means it will definitely not happen. They will do something dumber than the last two names. I don't know how, because only MS excels at this kind of thing in their own unique MS way.
This also makes way too much sense. There was a Xbox 360 Elite, but never just a Xbox Elite, plus the current premium controller is called the Xbox One Elite Controller so it would line up perfectly with that branding. It makes even more sense than my initial conclusion. Which is why it's even less likely to happen.