Only if they still exist in a few years. They wouldn't be the first company with a great IPO that didn't survive for long.
Kids don't use Facebook. They use Snap, for now. Who knows in a few years.
Twitter and Facebook are what their parents use.
Your comment reads as "nobody goes there anymore, it's too crowded".
Whether or not the people who bought those shares go under water isn't their problem.
AKA, the early investors are going to make way way more money than if they had sold to facebook.
https://www.theinformation.com/snap-changed-employee-lockup-...