I agree. By letting these "rumors" fly, many will leave on their own. Companies know that a certain amount of attrition will happen and this will thin out the employees naturally without them having to do a damn thing or pay anything. They allow employees to get bored and fearful and those employees usually leave on their own. If you've got a family and a mortgage, etc., then you may want to be proactive and not wait to be laid off, but if you can get by if a layoff does happen, why not collect the payout and look for a job after you know for sure you are out of a job. In other words ride out the rumors and see what happens. Maybe you are one of the ones that they keep.
Remember, many will leave after 2-3 years anyway because that is the nature of things with or without a looming layoff. People get bored or don't feel their career is growing fast enough and they go where the best money is.
Even if you get another job somewhere, you could be in the same situation so no matter what you choose to do, look now or wait and see if you get laid off, there are simply no guarantees in life.