You don't need eminent domain to build high rises. Developers can easily make very compelling offers to those currently in small houses to get them to move.
This article http://newyorkyimby.com/2015/01/the-yimby-report-2014-adds-a... suggests that in 2014, NYC added 44.8k units and in 2013 it added 22.9k units -- call it an average of 34k units.
This article http://sf.curbed.com/2015/7/16/9939720/sf-is-set-to-add-more... suggests that SF is adding about 3.6k units per year right now.
And NYC is 10x the population of SF. So. Sounds like they're expanding at around the same rate. (NYC is only 6.2x the land area of SF).