You can do it. Anandtech did it. But kiss your warranty goodbye. Which is why I am reluctant to do it myself when I get one.
3 yrs down the line... maybe. I mean, I can fix most things but I can't fix a motherboard and the power supply isn't really standard. Those are two things I would be concerned with if I didn't have a warranty.
If you can wait, do so. Since there may be updates ina few months. PRice drops on chips are coming as well, so we could see an all eight-core lineup. Although I am beginning to question the likelihood of that.