I'll be really interested to see what the electro-optical component does! Just hope is it more affordable and useful than diffractive optics proved to be in practice.
meanwhile there are Sigma zooms that go to 500mm featuring OS that weigh in under 2 kilos; I don't think there's any reason a canon 500 f/5.6 L IS prime lens should be any heavier.Sigma uses a trick of making their 50-500 and 150-500 zooms f/6.3 at the long end. That smaller aperture does help bring the size, and consequently cost down too. Then throw in the usual build quality considerations.