It will take at least 3 months for any such shortage to appear. But I don't anticipate there will be one. Some people will buy up more kin houses, it's true, but many people have houses purely for storage, and now that houses have the new, expandable storage system, the only real advantage to having a kin house over a regular house is the ability to decorate a larger space. Some people will want that, some won't. Those who really want extra kin houses will have gone to the effort to get them already (I currently have 4). In fact, most people who want multiple houses will have already done that too, via creating extra accounts. Also, a lot of people will want to keep their characters in the kins they are currently in, rather than be out on their own. No kin chat, no shared name under their own, etc.
With the housing system supposedly changing later in the year (Not going to hold my breath any longer), all of this could be changing again anyway.