I would assume that your assessment is correct--Office 2007 doesn't get more updates but is still usable, and I don't think Microsoft DRMs their software in such a way that they could kill the product outright anyway. Whether you want to keep using Office 2007 or not is another question--with no more updates also comes the lack of security updates, so while not "dangerous" in of itself, using an unsupported product means foregoing security patches in response to more recent attack vectors.