This is the way IK Obi paints iPads and similar devices, as compact but still-powerful computing platforms. He's right, but aside from having powerful CPUs and capable of hosting lots of RAM, that's where the parallels end.
An iPad is a closed system. There is no add-on hardware that doesn't connect through the single I/O port and isn't subject to that port's limitations. USB is implemented in software and suffers from the high latency you'd expect. Analog to digital conversion is also implemented in software. There is no audio I/O except for the 1/8" jack meant for telephone headsets and earbuds. Disk drives are slow and limited in capacity (anyone seen a 3TB iPad?).
While such limitations don't preclude many applications, they fall short of what we've come to expect in a DAW. Most of us have multiple terabytes of storage. Most of us have high-speed USB or Firewire interfaces. Most of us use phantom-powered microphones. Most of us are accustomed to multiple audio inputs and outputs, and balanced connections. Most of us prefer large video displays and many have two or more. Most of us use MIDI, at least occasionally, and those who do want 6ms or less latency. Some of us use dedicated hardware DSP processors. Most of us burn CDs from time to time, or back up projects to DVDs. Many of us need separate cue mixes or at least multiple headphone outputs.
Say goodbye to all of these things in an iPad-does-everything world.