Doubling the wards would ideally give roughly 60-65% of active characters eligible to own housing (since you have to be level 50 to buy one) a house, but this doesn't account for Free Companies. And the more the playerbase grows on each server, the more of an issue sticking to Ward housing is going to be.

I would honestly suggest transforming the current 12 wards into FC only housing. Then adding a 13th Ward with plots that are decorated, but each one leads to an unlimited amount of instanced plots, similar to how apartments and FC rooms function. The plots in the 13th Ward would be for personal housing, and could theoretically be unlimited in number like apartments can be. Because the plots would be instanced (yard and interior of the house), and not constantly running like the wards are right now. That alone would take a strain off of the server memory. SE also needs to implement a "one house per server per account" rule to prevent individuals from taking up 16 plots on one account (8 characters, each with 1 personal house and 1 FC house).

The more the game grows, the more limited housing is going to become. Even with people relinquishing plots. Because it is in extremely high demand, and there just isn't enough supply to meet the demand.