A naive "duplicate" feature would operate by copying the entirety of tablet A onto tablet B. Certainly the worst case is /very close/ to this even if we're quite clever about it and copy only the user's data and preferences.
The largest Nexus devices are currently 32GB I believe. On a GigE link, with a fast enough TCP/IP implementation (neither of which is available on any tablet today) that's maybe six minutes of data under ideal circumstances.
At a (slightly) more realistic 50Mbit high speed local WiFi it will take more than two hours. At that point you're definitely asking the user to plug everything into the mains, and find something else to do while they wait.
But our esteemed editor suggests NFC. I suspect he has not tried doing very much with NFC, because the target usable bandwidth is less than a megabit. Copying one tablet's contents onto another can be expected to take as much as a fortnight, and of course any real user would long before that grow tired of the "Please wait..." message and give up.