It's not impossible to get a house but it is definitely difficult on most worlds (I haven't visited the JP worlds for several weeks, a couple of them might still have houses left).

It's extremely unlikely you'll be able to buy a medium house directly. You'd be much better off buying whatever small you can find so if a medium does become available you can relocate to it. It will cost you a bit more but it will improve your chances of getting what you want.

Demolition timers were reactivated with 5.4's release on December 8th. Sometime on January 22nd, we should see a small surge in available houses as the 45 day timer will end on those plots with owners who stopped playing during the demolition suspension and never returned. There's always the chance that a few houses might become available before then so it doesn't hurt to be looking daily.