Aluminum bodies will become common, (at least on trucks), because government mandates for fuel mileage, have left manufacturers no where else to turn. And, they will increase the cost of vehicles, insurance, and vehicle repairs.
As stated, there have been aluminum panels used to some degree on larger vehicles for some time.
With few exceptions, damaged aluminum panels are more difficult to fix, resulting in more panels being replaced, rather than repaired.
Replacement aluminum panels are always more expensive than steel ones. Some are really expensive.
Replacement of aluminum structural body panels, (welded stuff), is really expensive.
As far as corrosion goes, the aluminum panels corrode too. Which will also be more expensive to repair.