Any idea what this will mean to people applying from the United States?
No idea (this is the first anyone will know of it), although they've only recently changed the settlement visa processing to Sheffield, and US biometrics are already done by US immigration so I'm not sure there's much that will be changed.
I supposed they may set up more places in the US for all other visa applications, as up to a couple of years ago, applications were processed by UKBA in Chicago and LA, as well as NYC.
I would suspect this is more likely to affect countries which have no UKBA consulates or application centres at all yet. At the moment, those people have to send their applications to other countries for processing (i.e. some Central American countries have to send their applications to NYC for processing), so maybe they will bring in application centres for more countries.