I have a problem with "evaluating" a lens only from reading reviews
I'd rather listen to the owner's experience, and I've seen some quite good images taken with it.
By the way, to quote from the review: "This lens is already quite sharp wide-open, and it becomes very sharp and contrasty when stopped down to F8."
As a Pentaxian, I want Pentax to do better. I'm even helping them with my money
But calling the DA 560mm "crappy" is nothing more than bashing. We can agree it's an imperfect lens, and on the necessity of replacement.
One of the reasons I'm biased against Pentax rebadging more Tamrons is people are now assuming that every single Pentax lens is a rebadge. I admit not being entirely objective about this.
But the root cause - brand dilution, as opposed to regaining their prestige of a top lens manufacturer - is a real issue.
There's also the matter of offering something not available to the competition, especially not available at lower prices (as would surely be the case). There's also the matter of re-gaining expertise in this niche, patents, etc. to make possible more ambitious designs.
Sigma never said they no longer want to serve the K-mount (although I don't see any sign of new K-mount products from their side).
I think they're more likely to launch (on their own) a K-mount super tele zoom than Tamron. But it doesn't matter which of them would be doing it.
As for writing something more positive... that's easy: just remember the subject of this thread. A D FA* 50mm f/1.4 on schedule for a Spring launch - top-end lens, with a ring-type SDM motor; a DA* 11-18mm f/2.8 on schedule for a Summer launch; that means they're not abandoning the high-end APS-C.
By the way, those D FA* lenses make me slightly more confident about some future super teles.