I think that's fine. I dont think the point of this is to confiscate land that people own and build condos on it. But realistically real estate ownership is pretty disperse, even in small town called Atherton there are going to be thousands of individuals that own 1 acre plots and maybe a hundred that own larger plots. It just takes a couple people to choose to sell their land or to die.
And the average home in America is owned for what, like 5-7 years? If someone is moving out of the community, are they really going to ignore a windfall payment from a developer?
And how about estate sales? Are the out-of-state heirs going to care to who their parent's property is sold? Or are they just going to go for the top dollar?
Put me on team top dollar. Hell, I'd even consider accepting a lower offer from a developer if I knew they were gonna build more properties in it (though of course this is extremely unlikely to happen as the developer planning on building more units stands to make more profit and the land is thus worth more to them).