During 2013 to 2015 the CERN Axion Solar Telescope (CAST) has effectuated its final phase of solar axion searches providing a world leading limit on the axion photon coupling strength for ma< 0.02 eV. This sensitivity has been reached thanks to the development of novel detection systems, notably new Micromegas detectors with lower background levels, as well as a new X-Ray Telescope built specifically for axion searches. The background level achieved is below 10-6 keV-1 cm-2 s-1. These innovations serve as pathfindnders for a possible next-generation axion helioscope, notably the proposed International Axion Observatory (IAXO). The planned developments of the Micromegas IAXO detectors will also be shown.