Two Micromegas chambers of 1 m2 size and 1 cm2 cell segmentation have recently been built. Designed for Particle-Flow hadron calorimetry, each chamber features ten thousand channels with embedded front-end electronics and three readout thresholds (concept of semi-digital hadron calorimeter or SDHCAL). The chambers have been tested in a muon beam and also exposed to hadron showers inside a steel structure. Excellent performance such as low noise, high efficiency and very uniform spatial response have been measured and will be reported. The measurements will be confronted to the predictions of a Monte Carlo simulation for which a complete digitisation procedure has been established. Finally, prospects towards the use of a Micromegas SDHCAL at a future linear collider will be discussed based on the scalability of current prototypes to larger sizes and on the expected energy resolution and linearity of such a device.