I think you've got to look at that number as something to set the tablets apart from the mobile lineup, or (more likely, imo) as the top end of the new product range as we've alluded to here. Just a guess, though.
Dropped it too often--USB connection no longer works, and when on calls, nobody can hear me speak. Too scratched up to stay in warranty. ****.
What if the next ten are all 4 digits? With the 1020 being the low end that was only expensive because it was released so early?
And the 1520 being mid-grade.
And the 1920 having a quad-core with 4 GB RAM and 128 GB storage space. 41 mpx camera with a dedicated camera chip. ...and Kinect.
Ok... Maybe I'm getting a little carried away