@sergio: I bet MS has access to some PS4 devkits, as well as Sony has access to Xone devkits. Perhaps through a third-party involvement. There is so much money on the line, it would be stupid not to check out the competition. They can't admit it though for legal reasons, but I would be surprised if no one at MS had laid their hands on a PS4 devkit.
That would break NDAs and open people to lawsuits.
As a programmer myself, there are things we tend to do to make sure we don't open the companies we work for to any lawsuits. I don't think Microsoft nor Sony would sanction trying to get the other's devkits prior to launch. Not even a, "we'll just turn our backs here and pretend you aren't doing what we told you not to do." No doubt once they are publicly available, they would get a hold of the other's released hardware.
There's a difference between telling a colleague friend an anecdote about how the two compare, versus actually giving them closed-door access to the system to compare for themselves.