I think you're overestimating the younger generation's exposure to technology. The Wii U and 3DS haven't really been the blockbuster sellers that previous game consoles have been, and really have not made it that deep into pop culture. Gamers will have them, but most teenagers are content playing on their phones. Most of them being iPhones, but even Android not all that commonly supporting (or needing) SD cards on every model.

And you're seriously misjudging how often a teenager needs to share a 5gb+ file... basically never. The days of pirating, ripping CDs, ripping DVDs and sharing them are basically over. If it's not on Netflix or Amazon, it's not worth sharing. And in the rare case, Dropbox does the trick.

Sure most teenagers are aware of flash drives and SD cards, in the same way teenagers 10 years ago were aware of floppy disks. They used them when school required them to, and haven't seen one since.