Looking at the Photozone vignetting test it seems at least this lens does not have the slightest problems in this regard and should also be capable to cover more.
Pentax-02 Standard Zoom 5-15mm f/2.8-4.5 (Pentax Q) - Review / Lens Test - Analysis
In comparison even a Nikon 1 standard zoom shows vignetting of above 1EV (at extremes).
This might be taken as an indicator, that a larger sensor might have been foreseen for future, also the lack of designation by mm and the naming as 01, 02 etc.
However, we will know when it's official, I would appreciate it.