[en] With the recent measurement of reactor mixing angle θ_1_3 the knowledge of neutrino oscillation parameters has improved significantly except the CP violating phase δ_C_P, mass hierarchy, and the octant of the atmospheric mixing angle θ_2_3. Many dedicated experiments are proposed to determine these parameters which may take at least 10 years from now to become operational. It is therefore very crucial to use the results from the existing experiments to see whether we can get even partial answers to these questions. In this paper we study the discovery potential of the ongoing NOνA and T2K experiments as well as the forthcoming T2HK experiment in addressing these questions. In particular, we evaluate the sensitivity of NOνA to determine neutrino mass hierarchy, octant degeneracy, and δ_C_P after running for its scheduled period of 3 years in neutrino mode and 3 years in antineutrino mode. We then extend the analysis to understand the discovery potential if the experiments will run for (5ν+5ν-bar) years and (7ν+3ν-bar) years. We also show how the sensitivity improves when we combine the data from NOνA, T2K, and T2HK experiments with different combinations of run period. The CP violation sensitivity is marginal for T2K and NOνA experiments even for ten-year data taking of NOνA. T2HK has a significance above 5σ for a fraction of two-fifths values of the δ_C_P space. We also find that δ_C_P can be determined to be better than 35°, 21°, and 9° for all values of δ_C_P for T2K, NOνA, and T2HK respectively.