CERN will temporarily shut down several accelerators, most noteably the LHC, and stop data acquisition for almost two years beginning mid November 2018.
According to current planning, upgrade works should begin on November 12, 2018 - practically one year from now. The end of the works is scheduled and recommissioning of the accelerators is planned for March 4, 2021.
This is part of a longer planning at CERN aimed to increase luminosity of the LHC acclerator, as well as increase the rate of data acquisition by re-designing the trigger mechanisms.