I work in Illinois, an employment-at-will state. My employers can fire me today and escort me out of the building for no reason at all, or any reason they choose, so long as it isn't discriminatory or illegal. Nothing is "guaranteed" in employment unless you have a legally enforceable contract.
The vast majority of people who quit do not get severance pay at all in this country. The employees you are discussing have the opportunity to remain employed until the end of the year AND get severance then. Personally, I think they should count themselves lucky, dust off their resumes and conduct a job search over the next 3 months, and get some books-on-tape to lessen the stress of a longer daily commute. Compared to tens of thousands of other people who find themselves suddenly laid off, driving some extra miles for 3 months while being forewarned and having adequate time to secure other employment in the meantime doesn't really seem like such a bad deal to me.
"Gratitude makes sense of our past, brings peace for today, and creates a vision for tomorrow." - Melody Beattie