Perhaps. But I see one of two things happening regardless: (1) the market maintains a distinction between real and synthetic or (2) the market doesn't, and diamonds become irrelevant as a luxury item.

If case 2 happens, it just means that diamonds get replaced with something else like gold, and gold luxury items become much more expensive. In any case, your future wife probably doesn't really want that massive synthetic diamond. It's a human thing, whether we (the HN crowd) think it's ridiculous or not.