We will review the results carried out on MeV blazars with both AGILE and Fermi, discussing open issues in this respect. The investigation of this kind of objects is crucial in constraining the contribution of the blazar population to the Extragalactic Gamma-ray Background (EGB). The estimation of this contribution is actually still debated, due to the blazar duty cycle and to the uncertainty of the percentage of unresolved blazars which are expected to contribute mostly to the low energy EGB ($< 400$ MeV). In order to achieve significant improvements in this study, gamma-ray telescopes with higher sensitivity in the energy range 10 MeV--1 GeV will be crucial. We will then present the concept study of next generation gamma-ray instruments (Gamma-Light, Gamma-400), aimed in particular at improving the Point Spread Function at lower energies (below 400 MeV). Gamma-Light and Gamma-400 will enable to detect variability at lower energies (E$....