I don't think these are similar at all and I believe antiques will increase in value in the near future.

Antiques have crashed in value and generally speaking their current price is much less than it used to be.

But I think that the same belief that makes millennials seek experiences rather than diamonds will eventually lead them to desire antiques. An antique is a symbol of experience, it encapsulates a time period, a belief system, a conception of art and when millennials become too old and have too many children/responsibilities to be able to go out and experience life they will want to purchase antiques as symbols of experience in their home.

The reason we don't want diamonds anymore is because they're seen as fake and inauthentic. Anyone with an Internet connection has read about the De Beers manipulation of the diamond market and has come to realise that diamonds are nothing but shiny rocks. Antiques, classic cars and fine wines etc. offer more than the opulent ostentation of diamonds they offer a story.

And you're crazy if you think art will crash. Its value as art has endured for centuries and its value in money laundering and related criminality will never end. People will always covet one of a kind art pieces