I personally hope they will do something like this, but with a pretty reasonable time-frame for being logged off. If, say, your account is completely unsubbed for six months or more, relinquish any houses that characters on that account might own. If you take a break for six months then all you'd have to do is sub for part of that time in order to keep the house, but if a player cancels a sub and doesn't return at all within half a year then it's probable that they aren't coming back or aren't interested enough in the game to be effected by not owning a personal house. But as long as they're allowed to collect their items if they do return and maybe even some amount of the cost returned to them then I see no reason why it shouldn't work.

Stretch it out to 9 months if people are in such a wad about losing their house, but honestly I think that even if you're that concerned about losing housing, you can at least sub for a month or two in the course of half a year even if you don't want to play or are not able to access the game for whatever reason. It would at least give players a way to hang on to what they've worked for, and weed out the ones that really aren't interested in continuing to play so that those on crowded servers who really want a house can have a chance at them too.