RSUs usually have an early termination date if an Employee leaves. Assuming an employee wants to leave but is unsure if their company will IPO before this early termination, will this employee lose all RSUs if the company does not IPO within that time?
Or are there other events that can help this employee maintain the equity they earned?
If your RSUs have vested and been released to you as real shares, then you can probably keep the shares. Some companies include the ability to repurchase even vested shares after termination, but in general, once shares are fully vested you can normally keep them.
Recently (the last 2-3 years) companies have been including a second Change in control / IPO trigger that must also be met before RSUs are fully vested. This is meant as a protection to both the company and the participant. The participant doesn't have to worry about a big tax event when the resulting shares will still be untradable. The company doesn;t have to worry about creating additional shareholders before the IPO.
If you have an award like this the company can generally cancel your units without compensation.