New possibility for further measurements of nucleon form factors at large momentum transfer in time-like region: $\bar{p}+p\to {\mathrm{\ell }}^{+}+{\mathrm{\ell }}^{-}$, $\mathrm{\ell }=e$ or $\mu$

We briefly summarize the status with electromagnetic nucleon form factors, and give in this framework, arguments to study the angular dependence of the differential cross section and single-spin polarization phenomena (polarized target or polarized beam) in $\bar{p}+p\to {\mathrm{\ell }}^{+}+{\mathrm{\ell }}^{-}$, in view of the availability of future antiproton beams.