There's been no announcement for a PC Beta yet, so i would imagine the result of this Beta will have no effect on the possibility of also a PC Beta entry. You should be safe
People need to be a little more careful with what they click on. The E-mail title clearly states, in capital letters "XBOX 360 Crysis 2 MP test invitation". If you can miss that, i fear for the safety of your computer what else you might click on during your browsing sessions.
I was expecting a sign up page or something of that sort with details about the test.