I see, hmm. Well, registering a domain does not cost much, and you will have
to renew it, which costs about the same as registering a completely new
domain. Of course there would be issues with old and new domain having
different addresses, which could be solved by redirecting traffic to the new
site.
The history has show that these kind of small projects like Trisquel are very
dependant of the main developer. For example BLAG effectively died when its
main developer just disappeared somewhere. Another example is Kongoni
GNU/Linux, which died after the main developer called it quits. Those were
examples of 100% Free Software distributions. I am sure more examples can be
found from not so free small developer communities.
So, it doesn't matter what libre distribution you chose, you are taking a big
risk if you count on that it will last next 10 years. That's why I might try
to figure out is there a way to make the domain and organisation not attached
to a certain distribution.