For those of you who are worried about lists, I highly doubt if they exists yet!. This is not how you do a sizable layoff, it is too difficult to create a list in advance containing thousand of names without it leaking all over the press and internet.
Real work will start once there is an official announcement. Power to be will announce % impacted, when will they do it and how it will be handled (transitional services etc) but don't expect HR to start knocking on your door on Thursday. Layoff are rarely based on performance ratings and mostly have to do with where they feel like they can cut people. In other words it is very likely that a 3 rating will survive and a 5 will be dispatched.
Disclaimer : I have no inside knowledge, and have no idea how big or little the number will be. All of the above is based on what I have seen during my tour of duty at other companies.