Currently, part of the high-eta [1.5 < |eta| < 2.4 ] region of the forward RPC muon system for the CMS experiment at the CERN LHC remains un-instrumented with RPCs. Given their performance as good spatial resolution, high rate capability, and radiation hardness, these micropattern gas detectors are an attractive option for simultaneously enhancing muon tracking and triggering capabilities. Since four years an international CMS GEM collaboration has been intensively studying the feasibility of covering the 1.5 < |eta| < 2.4 region of the muon endcaps with large-area triple-GEM detectors. Adding a suitable detector technology in to this region will be vital for the physics program as well as improving the trigger performance of CMS. Simulations and physics motivations will be presented. An overview of the latest advances in design, performance and validation tests for the first endcap station, the GE1/1 detectors, will be presented. In addition, initial ideas for Phase 2 upgrades in LS3 will be discussed.