Apple's paradigm is that the devices revolve around the main computer, and I don't see that changing. However, it could be that the "main computer" evolves into a headless thing (like the new Mac Mini Server) that auto-magically handles the Ethernet, USB devices, and mass storage for the iPad(s). Plug it into the wall, the router, and the printer, and it finds the iPad(s) via Bonjour on your wireless network. Your Mac Mini Server (MMS) downloads your upgrades for you, stores your media, and backs up your contacts and files. It works like a remote harddrive. Just drag files you don't need any more over to its home screen icon, and they're kept on the server now. It's also your hub to access your digital camera or other USB device, and shares them over 802.11n to the iPad(s).
Then, a few years later, when our Mobile Me accounts have like 5 TB limits and enough people have HD-streaming broadband, that computer can be replaced by a simple dock with an Ethernet port and USB for the printers and cameras. Apple's getting $99/year instead of $500 for the server, but still making bank. You buy stuff on iTunes and it automatically appears on your iDisk. You download it when you sync your iPad with your iDisk and put it in your iPad's library. Tired of that song? Throw it out on the iPad and download it again later.