i8 is the first but not the last of its kind, or at least that's what I hope.
Therefore, it's not inconceivable that as similar cars come to market, there will be an aftermarket sector producing thinner wheels which also aim to help with the aerodynamics as the stock i8 wheels.
One interesting thing I read somewhere is that, due to the extremely low CG of the i8, and relatively low body roll in corners, the i8 may have more grip per square inch of contact patch than a conventional sports car; hence, it doesn't need as wide a set of wheels as a comparable conventional sports car.
I can't wait to drive one and test out that theory.