I'd say the main reason behind Microsofts success this gen (besides the mistakes made by Sony) is the fact that Microsoft established itself as the "cool" console in the US. Microsoft turned the Xbox brand into something trendy. People follow that trend, especially now since they can play online with their friends.
That's why I don't see it likely for people to switch. Sony will win Europe and possibly Japan, and Microsoft will keep the US. People don't want to switch now. Not only do they have trophies/achievements, but people are just too stubborn. I hope i'm wrong on that front, and people will switch to whichever of the two puts out the most quality games, but I doubt it. Otherwise, things would be different this gen already.
I have my own personal beliefs as to why the US likes the 360 so much, but i'll keep them to myself as it would just anger people. What I will say though is I believe Microsoft will keep the US, and Sony will Keep Europe/Japan.













