Some people who were BNFs had their journals turned into memorials after they died, kielle is one. I think you have to ask Livejournal to do it? I read something on metafandom where people were talking about the idea of making a fandom equivalent of a will, so if you die, people will know whether you would want anyone to continue your fanfiction and what should be done with your Livejournal, etc. So if you wanted it to become a memorial you could ask