Well, Dave, the question is, will you give up your Nikon to go back to Pentax? Anybody willing to pay for Pentax FF? I mean, not the usual "if they offer this or that, I'll jump the boat!" - no "ifs" please, just, "hell yes, I've been waiting for Pentax all the last ten years, now I already preordered, even
- if the lens choice is not that big and third party lenses are dated or unavailable
- if all other accessoires are made for Canon or Nikon or from Sony
- if all RAW converters will take a little while to go Pentax - or I decide to use this fat DNG file format which usually wastes more disk space than anything else around except TIF
- if it remains questionable into which future we're steering: 60 year old mirror concept or mirrorless right now?"
Pentax once had gorgeous offerings for Professionals, the whole LX system was sort of on par with a Nikon F3 or better - but not many were interested. I don't know about the market share and for sure I'm not always happy with Nikon's decisions. But if it comes to Pentax, I'm done. Made my experiences and sold the whole stuff, never looked back. The screen is very innobative IMO - but that's just one detail. At least and after decades, articulated screen made it into a Nikon Pro DX, so it IS cool and usefull. But you're too late, Pentax. Again.
To answer your first question........No...simply the 4.4 Fps frame rate is pretty pedestrian and no good for nature........and I really don't need 36 Mps.......I like Pentax and the new K1 promises to be a great resolution camera......not to forget the pixel shifting mode which I think will equal medium format quality.....so keep your eyes out for the tests when they start to come in.
The 33 point AF.......well we will have to see..........up against the D750.......Hmmm...I don't think so!
1. Going Nikon is just a breath of fresh air for lenses, I wouldn't want to go back to the get what you given Pentax range with slow SDM motors and their problems, screw-drive is pretty snappy however. The best of the old FA* lenses have always held their price well, but now they will as expensive as the new Pentax/Tamrons. I just hope that Sigma panda a little to the PK mount to augment what is at the moment a pretty meager FF range. A camera system is as much about lenses as bodies.
The irony to that is my Pentacon is ready for Pentax and I'm modding it for Nikon!
2 Accessories are less of a problem.
3. RAW files with Pentax are all the same PEF/DNG. not like Nikon's.
4. I still think that DSLRs will still be the main stay of pro and prosumer cameras for the foreseeable future. (well certainly for me)
I hope Pentax do well with the K1 but it doesn't look like it will attract Canikonites.... DPreview's Pentax forum is on fire at the moment and it's good to see Pentaxians getting their crack of the whip for once!
All in all....Good luck Pentax and well done to have got the K1 to market!