The real impact of Google Fiber--assuming it doesn't get sued to oblivion by one of the other ISPs--is that it sets a new standard. Because Google is now providing better service than, say, AT&T, AT&T must now up their game to keep customers.

Thus, as Fiber rolls out to new areas, expect the pre-existing players to either improve their own services (to everyone's benefit) or try to undercut Google (to their own detriment).