Huh?
Joshua 1:1 Now after the death of Moses the servant of the LORD it came to pass, that the LORD spake unto Joshua the son of Nun, Moses' minister, saying,
2 Moses my servant is dead; now therefore arise, go over this Jordan, thou, and all this people, unto the land which I do give to them, even to the children of Israel.
The Assumption of Mary does not negate the fact that she, like Moses and Elijah, experienced death. Moses and Elijah, however, were seen with Jesus, all three very much alive, by the apostles. This is evidence of the assumption of Moses and Elijah.