Wow, cool. Some options, in order of likelyhood:
New Handheld - like the recent patent filings with interchangeable inputs.
Wii U Lite - with fresh look and smaller gamepad.
3DS Lite - fresh look.
New Home Console.
Those saying they wouldn't do it without a live conference seem to be missing the idea that Nintendo thinks the pre-recorded reveal is BETTER than the conference. I would expect all reveals to come by video now, including hardware. They aren't doing videos because they feel they have nothing.