My Sony a7iii and Sony hdr-nx80 both share the most advanced af systems I’ve ever used.
The wide area af with tones af points allow the cameras to track objects, pick out subjects and nail focus in situations where the k3 falls on its face.
As a long time pro, who preferred manual focus and back button spot af, I can telll you 100% my camcorder and mirrorless on full af can outperform the k3, and me.
Anywhere, any time and under any conditions.

Having admitted that...
The k3 is still every bit the great camera it always was...
An upgraded af system that brings up to. The same league as the class leaders wouldn’t hurt anything but your pride if you find yourself using full auto more than you’d have ever believed possible in the past.

K3 built in flash can act as controller or fill flash with hss if memory serves me correctly.
I’ve always preferred to use the off camera cable kit for hss.
If you want radio, you might consider the Godox system.
It’s astounding and affordable

Which newest Pentax flash?

as a video shooter I can attest that the image quality when you crop in from FF to APS-c on the a7III or the extended zoom function (same thing) on the NX80 there's no loss in quality... I have a custom button set up on my a7III to "zoom in" instantly.... when needed... on event shoots this means my 16-35 is the only lens I need...
I think it would be a great feature for stills photographers to have a custom function you set up just like bracketing focus and bracketing EV if you could have the camera "bracket" your cropping based the af sensors... nature and sports photographers would save some time in post that way.

here's a screen grab from an untouched file straight out of my pro camcorder.... I light my scenes carefully and try to get the look in camera as opposed to "fix it in post" so this is as intended to set the mood for the scene...
I have adaptors to use Pentax lenses with the sonya7III which has the same sensor as my camcorder, so I am hanging onto a few of my Pentax lenses

if you do switch brands and need to extend the life of your Pentax lenses....
you'll lose all automation and digital information between lens and body...but..
these Pentax to Sony adapters are the ones I own and they are great esp for video shooting:
this adapter comes in TWO varieties, one for kmount and one for DA lenses.... the DA version has a built in aperture ring that allows you to set the aperture on DA lenses. their marketing isn't clear so be careful to get the right one... Gobe
link you can set the sony a7III to shoot FF or Crop mode and for video, crop mode is still full 4k resolution....

While it cannot manually stop down aperture like the Gobe, the Fotodiox pro has two unique features... it acts as a variable extension tube for macro, and it has drop in behind the lens nd filters for video shooting...

BOTH of these can be had for about half the price of a Novaflex basic k adapter.
with the exception of the loss of AF these adapters turn the a7III into the mirrorless Pentax should have released 6 or 7 years ago.

or something dumb like like new paint job on an old model?
old model in a nice box with gold lettering?
hey they just released a new anniversary video featuring old cameras! What more do you want?

yeah about Canada Post... apparently delivery by sled dog is costly... it would cost me more to ship a pentax than I could sell it for used... hahaha!

For video production I shoot Multicam and use mostly Sony pro camcorders and now a Sony A7III

Well the other option is to toss the pentax out or give it away since no one in my area wants to buy Pentax, new or used...
the Pentax didn't stop taking pro quality images just becuase newer and better came along..it's just as good as it ever was... the problem is... I was forced to buy the Sony, and some Sony lenses, and new lighting...
as much as I hated the idea of buying replacements for lenses I already own...
I can't always lug two systems around....
I can still use the Pentax and prefer it for some jobs, like adventure and some studio stuff, it's about making excuses to keep using it more so than having to keep using it... anything the pentax can do, the sony can do too, not vice versa... having said all that... the k3 is a tank of a camera and I expect it would survive things that might damage or kill the sony... but in the event that my pentax does get destroyed while on an adventure shoot, or gets stolen... I assure you..the insurance money is going to sony not pentax when the k3 is eventually going to be retired or replaced...
knowing that decision is made, I do not buy ANYTHING pentax anymore... if my macro dies, gets broken or stolen... it'll be replaced with the native Sony, same with EVERYTHING else Pentax.
After k3, I waited and waited, then the K1 came out with crap for video specs, the decision to stop buying Pentax and start saving for Sony was made...

lens alone would not be enough to convince me to switch from Pentax, ( I know because I already switched from Pentax to Sony) .
Simply put... Pentax lenses generally are superb and usually value priced in their respective classes.
for example...
My WR DA 100mm macro.... I have an adapter with aperture control to use this lens on my Sony A7III. Why?
Two reasons:
a) in different macro lens shootouts the Pentax bested the 90mm Tamron and the Sony 90mm may be the highest rated macro on any system.. BUT it's not a huge jump ahead of the Tamron, meaning it's not edging the Pentax out by much...
b) I can live with manual focus for portraits and macro shooting, so whatever.... SONY 90mmm macro $1400.00 CDN, Pentax 100mm macro $649.00 CDN, Tamron 90 mm macro $949.00 CDN as of this writing...

Who cares if there's more options, with other brands when there's really only a few sensible choices?

having fewer choices isn't reason enough to switch, if the choices you have are generally excellent...

Pentax not offering pro video specs in ANY camera body..... THAT WAS REASON TO SWITCH!