I am wondering if a 4K version of this camera will ever be released, or if the FS7 has effectively already replaced it. Thoughts?

The FS7 can't replace the PMW300 because it has a huge sensor. The replacement for the PMW300 will have to have a sensor sized like the PMW300! Sony, are you listening?

At 1/2'', the laws of physics can't possibly produce a decent 4K image. At 2/3'', maybe... but they won't fit a 2/3'' sensor in the form factor of the PMW-300. Their 1'' sensor is a good balance, but right now their recording backend is crap. Panasonic for all we know is using the same sensor as the Z150 and putting 4K60p to good use.

Fujinon will have to make a 1'' lens for Sony cause Sony ain't touching the MFT 4/3'' market that Panasonic dominates in.

One nice thing about the laws of physics is that the Japanese are really good at working around them. Problem is that with the miniscule market for such a camera (wildlife videographers) they have no incentive.

I am not a wildlife videographer; but I do use my 300 for a variety of different jobs. Love everything about it except for the lack of 4K. I have two other cameras (GY-LS300 and GH4) that have large(er) sensors, though neither is in the class of the FS7. I have noticed FS7's on multi camera shoots lately, so obviously the big sensor isn't that much of a limiting factor for that camera. I know also that the FS7 has a great reputation, and seems to have become an industry standard for medium budget professionals. If money wasn't a concern, I would probably buy one.

So a Z150 sensor type camera in a PMW-300 form factor perhaps? I tried out the Z150 at a demo and liked it a lot, except that low light sensitivity was definitely lacking. Still, it seemed to gain up pretty cleanly, up to 9 or possibly 12db. The lens on the Z-150 is lacking compared to the 300, but it would be nice to have 18X instead of 14X. I don't usually have a need to use anything but the stock PMW-300 lens.

interesting putting a z150 up against a 300. i'm vaguely thinking of upgrading my trusty old ex1, not that i'm really into 4k (yet), nor have to deal with low light (thank goodness)...

so, is the general consensus that the z150 would give me a significant boost in picture quality over an ex1, bearing in mind it's price is pretty much in my budget range?

I can't answer your question directly. There must be a few who came from the EX1 who now have a Z150 so I'm sure they can offer a more useful perspective. But I can offer this:

I came from an EX3 to a PMW-300 (and I have also had a FS5 since 2015, as well as a Canon C100 since 2012).

EX3 was identical picture quality to EX1. PMW-300 was actually a bit improved on the EX1/EX1r and EX3 (lower s/n levels were quoted at the time of launch, 60dB as I recall), I guess due to more refined/improved signal processing that Sony used in the "second generation" PMW cams. It can of course also encode in XDCAM 4.2.2 at 50Mbps (and after a later firmware update at higher Mbps using XAVC if desired) rather than the 4.2.0 35Mbps XDCAM codec.

My view is that the PMW-300 has a noticeable (but not dramatic) improvement in picture quality over my old EX3. I love it for fast paced work where you just need to "get the shot". The viewfinder arrangement is excellent.

However, although I really like my PMW-300 but it's getting used less and less now that I have a FS5. This is for all sorts of reasons - one being the very significant improvement in picture quality the FS5 can get with it's s35 sensor, small/lightweight body and interchangeable lens form factor advantages. And the 4K is just the icing on the cake.

Whilst not in the same league as the FS5, I suspect the Z150 will be a step up from the old EX1 for picture quality - but I'll let others that have owned both confirm that.

I still have my old EX1 and now a Z150 and I would say the Z150 definitely has better picture quality. But the differences between the cameras are deeper than that. You get the 10-bit XAVC codec, 4K, continuous 120 fps slow motion in full HD, and a viewfinder that can actually be used for shooting. Not to mention the fact that the Z150 costs less than 1/2 what the EX1 cost when it was new. Because it is part of the XDCAM family, the EX1 has some operational advantages over the Z150 but a lot of people won't even notice or care about that. I'd like to sell my EX1 but it's probably not worth enough to bother with now.

I am still looking for a 4K replacement camera for my PMW-300, a camera that's capable of doing a wide variety of shooting. I have used the 300 for everything except documentary work, where it's 1/2" senor doesn't lend itself to shallow depth of field. The Z-150 may be a possibility, but I prefer doing doing everything manually and the iris, focus and zoom rings don't have the same "real lens" feel that the stock 300 lens does. Also, having to gain up so much in low-light concerns me. I know this is a Sony forum, but has anyone seen the Panasonic UX180? It appears to be a camera that's capable of doing a little bit of everything. It has a one inch sensor, a 20X lens that supposedly will go 24mm on the wide end (though I am not sure if that's in 4K), and costs $3,500. It may be slightly better in low-light than the Z-150. I don't believe it is capable of external 10 bit recording like the Z-150 is, which is a concern for broadcast work. Anyone tried it out?

Additional consideration should be given to the rise of a wide range of external recorders at affordable prices and decent form factors which can override the codec concerns of many of these choices.

I still shoot a lot of event work and occasional corporate work with my EX3 and love it for versatility out of the box. Yet, I find myself shoot more with an F3 and as of late FS7 with external recorder with much improved usability, longer runtimes at more economical card prices, faster downloads, and a single investment that cuts across many cameras. If the FS7 is out of price range, the F3 with slog update is readily available on the used market as a capable upgrade from the EX3 (F3 is HD, FS7 is 4K).

Good point about external recorders, especially since some of them have terrific monitors built in. What I am looking though for is a run and gun type camera that can be used for ENG, sports, theatrical performances, corporate work, etc. - which is what I use my 300 for now. But I am getting more requests for 4K, and as much as I love the 300, it's HD only. I love everything else about the camera. I wish Sony would provide some sort of upgrade path. Are you listening Sony?