The primary options I can think of that are not full acquisition are: - company buys back stock - VC sells on secondary market - IPO
The much more common and more likely option for these VCs to make the multiple or home run on their return is going to be to 10x+ their money by having a first or second tier cloud provider buy you.
I think there's a 10% chance that a deal with Google is done in the future, so their portfolio has Firebase for NoSQL and Firebase for SQL.