Just Call it Xbox 4 and never think about making stupid names again for the future ones.
No one cares what some delusional Marketing department thinks makes a Console sell, all it does it make it confusing as a name.
Xbox one is already stupid because now you have to call the first generation Console the Original Xbox to not confuse people when talking about it.
Funnily enough, confusion is a pretty standard sales technique. Buyers will (with the aid of the sales staff) often err towards the more expensive in some cases, because they have no idea if they really need it and they're afraid of being left with something that is, in some way, "inadequate". Or perhaps they'll panic and buy the cheaper one, be disappointed, sell it and buy a more expensive one.
You can guarantee that the proliferation of models (as "tiers") is designed to extract more money from those who can afford it, and make others stretch up a notch even if they
can't, strictly, afford it. It should also comfortably increase sales volume, if they price / spec the "base" model (and attached features / services) intelligently. Sony previously tried to offer a strong basic package at a slight premium, but I think now that the industry is geared up for tiered performance in the consoles, they will probably feel like they need to do exactly the same.
And it's for this reason that even the most ignorant of potential customers will almost never leave a shop with the original XBox instead of the latest, greatest and most expensive one available. Just think about how that conversation would play out with the sales staff. Likewise, on the internet, Microsoft and retailers alike will pay significant sums of money to make sure anything related to XBox will point to the latest and most likely greatest console.
It is pretty stupid naming, all the same. But then what else should we expect from an industry that likes to take a revisionist approach to the naming of game sequels?
One thing I'm personally banking on (what with the expansion of "tiers" of console performance within a "generation") is the continued blurring of lines between the consoles and PCs in general, as I'm well past due a PC upgrade.