Asus was originally testing the Padfone with Qualcomm's upcoming Snapdragon processor with the 28nm Krait core, but apparently it has decided to bet on something it has already tested in a working product, like NVIDIA's Tegra 3. The quad-core chip is used in the Asus Transformer Prime tablet, therefore it is not really a stretch to imagine Asus will be ready with the Padfone by spring.
The phone docking into a tablet concept is pretty novel and is sure to spark some interest and maybe earn Asus some more design awards like with its Eee Pad Transformer. Moreover, it should be a cheaper solution than buying both a standalone phone and a tablet, so bring it on. Needless to say, it also picks up girls if the below video promo is to be believed, just like Samsung's flexible tablet concept.