Physics motivations for future CERN accelerators

We summarize the physics motivations for future accelerators at CERN. We argue that (a) a luminosity upgrade for the LHC could provide good physics return for a relatively modest capital investment, (b) CLIC would provide excellent long-term perspectives within many speculative scenarios for physics beyond the Standard Model, (c) a Very Large Hadron Collider could provide the first opportunity to explore the energy range up to about 30 TeV, (d) a neutrino factory based on a muon storage ring would provide an exciting and complementary scientific programme and a muon collider could be an interesting later option.