A major reason why things look gloomy for another generation of colliders is that it’s not clear what to build. Electron-positron colliders like ILC/CLIC would be very expensive, and not necessarily get to energy levels above those reached by the LHC. They would be excellent tools for studying TeV-scale physics, but if the LHC has shown there’s no new physics there, the case for building them will be hard to make. Probably the best bet for going to higher energy is the HE-LHC, an LHC upgraded with higher field magnets. The technological limits on such magnets though will make it hard to go to dramatically higher energies. If no new physics besides the Higgs shows up at the LHC, there won’t be a good reason to expect it at HE-LHC energies. The case for the LHC was a slam-dunk, because we knew that the Higgs or something doing the same job had to be accessible at LHC energies. What there will be for an HE-LHC to study is less clear.