Often, buyouts terms are more generous than layoff terms. Even if the company has a history of generous layoff terms, the next one may be less generous.

The other thing to consider is if you'll want to keep working at the company after so many people have left due to the buyout and the layoff. If not, taking the buyout and looking for a new job is likely to be better for you than not taking the buyout, not getting laid off, and looking for a new job once you conclude you don't like the new environment. For one thing, you'll probably have buyout compensation and new job compensation at the same time; for another, it may be easier to find a new job if you're in the market before the layoffs increase the hiring pool.