Presented at the 2018 AGU Fall Meeting"The Soil Moisture and Ocean Salinity (SMOS) mission was launched in November 2009 and is still fully operational. The Aquarius Radiometer on board SAC-D was launched in June 2011 and operated until July 2015. Finally the Soil Moisture Active and Passive (SMAP) mission was launched in January 2015 and its radiometer has been fully operational. These three missions have a unique feature in common, that is an L band radiometer. For the first time - with SMOS - the globe was operationally covered with such measurement. L band measurements have enabled direct and "absolute" measurements of both soil moisture and sea surface salinity, opening up a wealth of new science venues and applications. L-band sea surface salinity data have significantly improved the knowledge of many ocean processes that were not well-understood before, such as river plumes, cross-shelf exchanges, mesoscale salinity fronts and eddies, and salinity signature of and contribution to tropical instability waves. They have greatly facilitated the studies of the linkages of the ocean with the water cycle. They have elucidated the relationships of ocean salinity with climate variability. Over land soil moisture measurements enabled to get access to root zone soil moisture, yield forecasts, flood risks, drought monitoring, improvement of rainfall estimates, etc. It is worthwhile noting that recently significant progresses were made in vegetation optical depth retrievals using SMOS paving the way to a new and very powerful vegetation index. Also worth mentioning is that the various disaggregation approaches providing typically 1 km spatial resolutions and very useful for pest control or irrigation management. Moreover, L-band measurements have also proved to have many other potential applications such as thin sea ice estimate (up to 50-100 cm) as well as freeze thaw dates, and potentially snow density and liquid water content. After all these successes it is crucial to carry on such measurements, key elements of the water cycle. User's requirements were almost unanimous in requesting at least characteristics similar to those of SMOS or SMAP. But, ideally, ground breaking results could be attained with a 10 km native spatial resolution. We will detail what the different options available to capitalise on acquired science results and propose a way forward.