Originally TS was saying housing improvement were going to be implemented in the 1 quarter of 2012, before whole "back to beta". I would say it would at least be that long.
If a game developer sets a release date for something, they always end up needing to postpone it to a later date. Some of them are catching on to that fact and wisely refraining from giving in to naive requests and demands for release dates.
Anyway, didn't your mother ever tell you that a watched pot never boils?
Put me down for April 16th, 2012!
(Just my pool bet. Do not take it as an official estimated date!)
But we just had a face to face meeting last week where we came to decisions on most of the feature. But to reiterate what @Wondermumbles said, until we're deep into it, any guess is just a guess, as its difficult to guess what sort of issues and edge cases will come up during the entire process. All we're certain of is that it's the biggest feature we've ever added to the game and it's gonna be months and months of work.