DVDs and CDS the same thing as far as most new drives are concern will be around for some time.
A Plastic disk that a laser had burn marks on will always be cheaper then ram memory by a large a very large margin.
Now as far as moving programs around networks up to the internet will always be cheaper then even a bit of plastic and is the wave of the future.
I in fact pick up two things first for my CD/DVD free notebook one was a USB DVD/CD burner and the second was a crossover cable to network my two computers together.
My USB memory cards are not a major way of transfer information between my computers.