In this article, the suitability of Nb3Sn to improve the performance of superconducting Radio-Frequency (RF)cavities is discussed. The use of Nb3Sn in RF cavitiesis recognized as an enabling technology to retain a veryhigh cavity quality factor (Q0) at 4.2 K and to significantly improve the cavity accelerating efficiency per unit length(Eacc). This potential arises through the fundamental properties of Nb3Sn. The properties that are extensively characterized in the literature are, however, mainly related to improvements in current carrying capacity (Jc) in the vortex state. Much less is available for the Meissner state, which is of key importance to cavities. Relevant data, available for the Meissner state is summarized, and it is shown how this already validates the use of Nb3Sn. In addition, missing knowledge is highlighted and suggestions are given for further Meissner state specific research.