They may be bought by someone bigger and then shutdown to protect the existing wild gardens. There are many analogies. Astrid[0][1] and Wunderlist[2] come to my mind.
[0] https://en.wikipedia.org/wiki/Astrid_(application)
[0] https://en.wikipedia.org/wiki/Astrid_(application)
Newell said that there was a better chance that Valve would “disintegrate,” its independent-minded workers scattering, than that it would ever be sold.
https://www.nytimes.com/2012/09/09/technology/valve-a-video-...
The difference here between Valve and most all of the infamous tech buyouts of history is Valve has no VCs looking to cash out who get final say, or public investors looking to maximize returns.