Maybe the most interesting concept unveiled at the Mobile World Congress is the Asus PadFone. Basically, it is based around a 4.3-inch Android smartphone, that can be docked into a 10.1-inch tablet. This converts the smartphone into a tablet. The tablet can be docked into keyboard, which converts the tablet into a laptop. Each dock adds a supplemental battery and storage.
How popular this concept will be depends a lot on how much the whole system would cost, but it should be a lot cheaper than buying a smartphone, tablet and laptop separately.
Combined with concepts like Ubuntu for Android or used in conjunction with Windows 8, Asus scalable hardware could be very interesting indeed.