Look, here's the deal, these missionaries won't really be able to convert bahuns/chettris and other "hardened" castes out there much. So yeah, they will definitely convert the mostly Buddhist folks, and maybe lower castes as well. I think that Nepal will remain a Hindu majority no matter how much they try their "magic", in the short term. Long term, it's another story. Hinduism will die out in a couple of centuries, at least in Nepal. I think our tolerance is our demise.