Higgs boson was predicted in theory in 1964, and found in LHC in CERN in 2012-2013. With this, all elementary particles in the standard model of particle physics have been found.
From the 1970s to 2010s, physicists believed in a theory called supersymmetry, which predicted supersymmetric partner particles for the known elementary particles. But these should have been already found in the energies used in LHC.
For the first time, there is no mainstream theory that would predict any new findings. Maybe the next bigger particle collider will find no new particles at all?