A stopgap measure may just be exactly MS's plan. Although of course they would never admit it, but technology wise it would be. If the specs are true it's definitely an interesting strategy.
Basically, get a mildly higher spec'd Xbox 3a out there to take on Wii U, expand their Kinect casual market, and probably offer more online connectivity features at a breakeven or small profit at launch. Then 4-5 years later in 2017, launch the true Xbox successor with all of the above plus a significant spec bump on matured processes. It kind of singles out Sony, and I'm thinking they're betting on the chance that any advantage of Sony bringing out a more powerful box in 2014 would be marginalized. In any case they'd still be raking in profits with at-cost, low spec reliable hardware. And if PS4 does sway things back in Sony's direction, Xbox 4 in 2017 would hamper that imo.
They could very well adopt an Apple strategy here...
Ms could say offer a biennial updated console (enough time to ensure process shrinks available to support ~2x increased hardware for the same msrp)
Increase the ram, along with the rest of the guts and ensuring that software is forward compatible, games would take advantage of the increased spec in some way or another to encourage adoption of the new console, while still being compatible with the original model.
This means MS could afford to be less aggressive on selling for a significant loss as they do now, while at the same time, never being fully outclassed by any competing hardware. This would also mean the MSRP out the gate wouldn't have to be astronomical either.
OR, they could adopt this approach right out the gate and have a true "Core" unit, and a true Premium/Elite unit as the other multi-sku rumor suggested.
Such an arrangement would put a lot less pressure on end-of-life console production hardware and software and the same for "NG launch" hardware and software.
If a consumer is feeling the console is getting a bit long in the tooth and would like to see an "upgrade", they can simply buy the next version. Or if they're happy with having 7 year old hardware *ahem* they can still game on the ancient console!
I'd love to see some variation of this. Either with the console directly, or with a PC-centric core standard. Preferably with the console as PC gaming in general is a headache.
Of course, such a concept would mean "scaling the hardware" ... and we know how some around here don't like that idea ...