Now... are you really sure you're completely impervious to brand loyalty?
For instance, would you consider permanently blacking out the name on your Pentax?
After all... it's just a name and that name plate doesn't really add to the IQ.
It seems to me that we don't have enough evidence to make a definitive statement about the new Pentax zoom. All of this is purely speculation and we'll only know for certain when the lens is actually out there, tested in the field and on the bench. For my part, I purposely bought a Pentax camera and I intend to buy into the Pentax system. I've always admired Pentax optics having had several friends with Pentax systems. I, however, was deeply committed to another line and therefore could not indulge myself (until now). I have full intentions of getting the Pentax zoom when it is released UNLESS there is a huge difference that I believe I simply cannot justify. I suspect the IQ will be better than that of the Tamron but only time will tell.
All the best.