Just a matter of limited resources for Pentax to do too much all at once.
To be fair, they do have the DFA15-30 that should tide any 'serious' landscape shooter over till primes are released. ('serious' also mean that they would be willing to fork up the cash for that penultimate performance and versatility of the zoom
)
IMHO, there are enough old and new options out there that I can't be bothered to wait or over think it.
The Samyang 14/2.8 works good on the cheap end of things, and the Irix 15/2.4 and Laowa 12/2.8 are good too at the more expensive end.
There are older lenses that work well if one can get a good copy, like the FA20/2.8, FA20-35/4, FA28/2.8, K28/3.5.
More modern ones like the FA31ltd.
In fact, the inexpensive DFA28-105 works really well as a landscape lens (as a wide 28mm and more of course)