@massivelyop letting all "sunset" or "maintenance mode" vocabulary apart (who likes being remembered that MMOs are not eternal?), I'd say "reboot", because it means that they'll serve a totally different game under the same name ("revamp" having the same feel, when it touches a part you're active in)(the word is also scary on the literal sense, because it means downtime - and sometimes a whole week-end of it...)
@massivelyop I, uhh, have actually had this happen to me. Multiple times too! All three times this has happened to me, I ended up just spinning up a new account, and stopped spending money on the game.
@massivelyop I have an alt in #LOTRO currently hanging out in an umbari tavern, not doing anything save an occasional slaying of crocodile, sounds like a decent life to live :) (I wouldn't be in the boots of my main, though, who's wandering through the sewe... err the under-city)