Average users don't care enough about security to educate themselves and seek out solutions to potential problems proactively. The mass internet worms were a result of patches that were up to a year old not being applied to systems in a timely manner.
What makes you think they'll actively seek out a new browser?
As far as privacy goes, without getting political, users don't have clue #1 about privacy.
I agree with Roger that it may gain steam if OEMs install it - but they'd need to uninstall IE first.