While I understand why people want it to be retroactive, it just isn't fair for people who got it when it was totally allowed.

Besides, in the long run it won't really matter if some people are grandfathered in. Those people won't be able to buy more houses, so the new wards will be for those who can. There will be more wards over time.

Furthermore if any of those people with multiple houses go away and get demo'd, they'd lose their houses that way and I'm pretty sure (though it's not confirmed, but based on how the system sounds like) that they would end up with the 1 house rule once that happens.