Infrastructure...

http://www.treehugger.com/cars/kitakyushu-where-does-your-old-used-car-end-up.html
So the city evolves.
If we move the cars out, and enrich the walking experience of the city, what happens next? 
The street front then become less important, maybe the shopping experience moves out into the street.  The surface that once was a road becomes something freed from the shackles of the car.  It becomes a stage for food, cafe's, shops, performance spaces, cultural exchange, or something much more.  
http://www.euaustralia.com/2008/01/
It becomes a new way of experiencing a city.  The shop fronts then become less important; they maybe become the walkway themselves, opening up the shops once located within, out into the sunshine and fresh air.
http://www.actbus.net/forum/index.php?topic=963.0
But for this to happen, there needs to be a shift away from how the city works now into something else.  We need more infrastructure to support such a move, one that focuses on mass-transit rather than the car.  Gone will be the express-way's into the city, replaced by train lines and bus way's.  There would need to be suburban hubs where people can gather with express arteries into the city; while a whole network of other mass-transit options are needed to service pedestrians to the hubs.  And this is where a relatively cheap option of clearing the streets of cars becomes very expensive for a city that already lacks sustainable mass-transit.  It is at its maximum ability to service the city now, and the population will only increase exponentially. There are commuters from over 100km's away that need options, and unlike other major cities in Australia, we lack a train connection to most of these commuters.  What would be a beautiful idea needs support from government to re-invent the mass-transit for the whole south east of the state.
http://www.creative-va.com/workvirtual.html
Not that this cannot be done.  But if you get rid of the cars for the sake of the pedestrian spaces left behind, why not another idea.
Why not get rid of the need to even commute to the city or anywhere for that matter?
We already acknowledge that the online retail market is booming, and virtual technologies are fast become a reality; then what about not having to go to work at all?
Do we need to worry about a few streets for pedestrians when we can revolutionize the need for a city at all?