1. Microsoft is not switching over to GDDR5.
2. ES RAM + DDR3 was a decision made years ago to balance profitability and developer requests.
3. Increasing RAM count has little benefit, but can be done.
4. There will be no drastic changes in RAM type. You will not see DDR3 suddenly change into GDDR5 or stacked memory. Unless you want Microsoft to spend another $500 million and to launch in 2014.
5. Microsoft's machine is better designed in terms of profitability.