There is a 30~50% difference in term of hardware power. That fact will never change.
The mistake is to think that optimization closes this gap. The SDK is 10% faster, you add DX11, let's say 5%, etc. and then magically after a lot of announces like that the gap disappeared.
The SDK improvements does not close the gap between hardware, it closes the gap between the hardware power potential and the power actually used in software for this hardware. If there is a similar level of optimization on the concurrent hardware, the gap does not change at all. If there is more potential for optimization on the concurrent hardware (and that's something we can't tell) the gap would even go bigger.
As for the cloud, so far is mostly BS. If it became something great, it could be replicated anytime by competition. MS doesn't offer a "power of the cloud's secret sauce", it offers a distant calculation service. That's it. There are lot of services like that, and it has quite a lot of cons. Cost : you have to pay for the service, even for a single player game you are selling for years. And efficiency : most game calculation can't adjust with network speed.







