If something replaced cocaine, my guess would be pills, both repurposed medical grade ones and things like ecstasy. Being completely manufactured allows for an arbitrary distinction in quality based on packaging, and that's obviously something people like to buy into.

That said, I'm not sure I believe cocaine ever lost favor with the wealthy. Maybe they just shifted from open semi-public use to more private and small groups doing it within the whole? Instead of open use in the big common room, maybe people just split off into side rooms in small groups that are interested to do it and rejoin the main group later.