I spent years years/campaigning on forums "for" new Pentax lenses,
.... for a while things were looking promising, with Sigma bringing out new models and Tamron, Samyang have served Pentax well, then things turned, Sigma's latest lenses "stopped" being shod in the K mount, Tamron "stopped" the K mount with the newbies, Samyang still does "mostly".
One thing to remember is having changed to Nikon does not mean falling all over Nikon's range of lenses either!!!, since the D7100 bought S/H, I've only bought the D750 and the D500 bodies and they are grey market!....
Since shooting Nikon I've not bought one new Nikon lens!
I've have however bought 10 "S/H" Nikor lenses.......two Tamrons, 150-600mm (2nd G2) and one Samyang 14mm F2.8. So I haven't been lining Nikon's pockets that much either.
The point being is, I spent time trying to rally Pentaxians to constantly reclaim new lenses and also hoped that Pentax would attract the eyes of TamSig to provide their new models with the K mount, frankly I'm not worried if I shoot with a 500/600mm lens whether it has Sigma or Tokina, Pentax or Mr. Kipling written on it, as long as it's a good lens.
A shooting system is all about lens availability...many great lenses are coming from Sigma/Tamron and others, I want access to those lenses, with Nikon you have it with Pentax you don't, at least not the recent ones.
To close, I want Pentax to bring out some new lenses or at least rebadge Tamron ones, maybe till they can bring out their own, I suggest some here:
Tamron G2 ......I said enough about this lens.....a game changer!
Tamron 85mm F1.8......a great portrait lens that's is missing for the K1 (Pentax used to make the FA* 85 mm F1.4..a great lens it "was" too)......... Pentax do not have a FF portrait lens, like come on?
Sigma 24mm F1.4 Art ..... again for APSc and FF
Sigma 20mm F1.4 Art...... "" " " "
Just those four lenses would change so much for Pentaxians, I want Pentax to be great again I really do....so,
Pentax bring out the lenses even if some are rebadged, they could be brought to the market within a year.......then all these stories could be for the history books!
PS, Sigma does have the 150-500mm and the 50-500mm new in the K mount, the 500mm F4.5 in the K mount "was" also available in the K mount, I think it's now discontinued but can be found S/H!