It doesn't matter. If factory diamonds are cheap, the tacky hoi polloi will slap them on everything Swarovski-style, the appearance of diamond will no longer connote wealth, and the wealthy will drop them like a… rock.
This is on-point. Cultured gemstone-grade diamonds started becoming viable in the early '10s, and manufacturers were careful to provide better value than mined gemstones but not overly sell on it, instead stressing the ethical aspect of CVD/HPHT-treated stones. In addition, the process wasn't yet refined enough to undercut traditionally-mined diamonds by too much. If that changes, then the meaning of diamonds to the rich will as well.