The CMB (Cosmic Microwave Background) polarization community is coming to a decision point about the future direction of the field. On the one hand, the astro2010 decadal committee endorsed a technology program leading to a post-2020 satellite experiment. However the committee also supported a medium-scale initiative for a ground-based program. To capture the full scientific potential of CMB polarization, the CMB community must develop new observational and theoretical capabilities. Our study program aims at identifying the optimal combination of future ground-based and space-borne experiments in order to produce timely and definitive results.