The 2 "usb holes" in the back are for none other than plugging 2 usb devices into! Of course you can plug your ipod into them! You can plug anything you want into them. Nothing will work besides the wired LAN adapter, but you can still plug it in.
You can't tell me that you expected Nintendo to release everything at launch. They put the USB ports there not knowing what would plug into them, but when they do come around to releasing new hardware, there will be way of connecting it.
So far the ethernet cable plugs in, but that my friend is only the start.