Question About Guild Halls
Anet has said that upgrades will carry over. Treasury should be safe too.
Also when we do capture it, do we have to reclaim each hall every time if we want to switch back?
Yes, and you will have to pay the 100g needed for starting the expedition every time you want to switch.
Source: https://forum-en.gw2archive.eu/forum/game/hot/Day-Six-Guild-Hall-Statistics/first#post5679436
RoF