No they should not upgrade the old raid weapons. What they should do is get rid of vanguard gear that takes you to 31 (I think it should take you to 28 max and shouldn't cost ascendant material to upgrade). You shouldn't let people skip raids and get near max level for just doing strikes. The strike playlists should be a stepping stone into VoG, which in turn, should be a stepping stone into CE. That way you don't make the old raids irrelevant.