Well Xbox is the brand, that's the word that needs to be in there somewhere. So like apple's phones are the iPhone 3, iPhone 3gs, iPhone 4s, etc (iPhone is the brand, postfix is the model), Microsoft can keep the Xbox prefix there. Personally I think the reusable platform is the direction they will go next gen, it just makes sense given how many devices they have out there, how many more they will have, how many more markets there are to grow into (cars, etc), and how to me it behooves them to make it easy for coders to get their code working on every device and hence give coders a piece of every possible revenue stream in as simple a way as possible. I like that with xna already, I just put out a game for Windows Phone and I can easily recompile it to work on Xbox 360 and PC today, and presumably tablet tomorrow. That's just a really nice advantage. What I'm curious about is how they will handle the transition from the 360. I don't think they had this all planned out at the time of the 360...whereas I expect Xbox Next to have the platform strategy in mind from day one so future hardware upgrades will be easier. Maybe they will offer "360 greatest hits" as downloadables, to where publishers can rebuild games to make sure they are compatible with Xbox Next, and have them as digital download only. Who knows, but that's the step I'm curious to see how they handle.
If they are following the Apple model then they'll have to also follow their MO in only upgrading things which make a difference to the majority of end users. Kinect and the console redesign on the outside both made a huge difference for the end users.
They can certainly continue to upgrade the internals, however they'll likely only upgrade minimally as far as it would take to improve the user experiences for the majority of use cases. At minimum they'd likely need to increase the bandwidth and processing power available to Kinect, improve multitasking if they want to follow on with what Nintendo are doing and perhaps clean up the visuals and offer a default 3D option. Effectively they could do all that with just a Wii-esque upgrade.
The other advantage to going with a long term platform strategy is they don't have to put all their eggs in one basket. Nothing stops them from releasing two sku's, a low end 6670 model for $199 and a high end 7950 model for $399. Unlike the old console model you can get royally screwed if people don't buy your expensive model as Sony painfully learned. But this way if they don't buy the $399 model then no big deal, there is still a $199 model that plays everything. I think they need to keep this in mind as the hardcore gamers are no longer the ones driving growth.
Would it be a good option to simply offer a more up to date Xbox 360 this year and follow on next year or 2014 that with a true next generation successor? If they want to keep the 360 on the market they may as well give in an overhaul so it can last another 5-6 years on its own. They can then initially split the market between media people/occasional gamers/etc towards the cheaper, older box and let the early adopters have access to their new and improved version in the following year. This is similar to the PS2/PS3 split except they'd be making moves to keep the 'PS2' viable as it's own entity.
So in a nutshell:
4 cores vs 3 with extra cache
480SP 'turks' core or equivalent, both on 28nm
1024MB GDDR5 @ ~70-80GB/S
Better USB bandwidth.
16GB flash
Blu Ray support for triple layer discs (forward compatible)
HDMI 1.4a
Blu Tooth and signalling hardware for possible tablets.
RRP: $299-$499 depending on HDD/Kinect
Xbox 360: cut the price to $129/149 and then decide later what to do with the legacy console.