Will X-T5 video quality be worse than X-T3/4?

JNR wrote:

I never made any reference to the pixel density, nor the oversampling - so you're guessing that I don't get it. In reality, if you do a test, you will find that the various X-T cameras perform best in sharpness and lack of artifacts at 2k... but you are buying into the "my amp goes to 11" marketing gimmick.

We haven't been told the heat tolerance of the T5, so it is anyone's guess if it is better or worse than the T3 or T4. We do know (based on CIPA rating) that the T5 uses less energy, so likely generates less heat than the T4.... So, very possibly the T5 could outperform the T4 on that measure.

The other thing I should have mentioned is the lower ISO @ 125 yields greater DR and lower noise. This is especially beneficial for FLOG and FLOG 2 which rely on higher ISO (2x-3x), allowing for presumed lower noise - but again this is just a best guess based on specs for what is still a pre-production camera. But don't be surprised if it performs quite impressively - at least for shorter clips - which is what most stills shooters are going to want for the occasional video.

You specifically wrote:

...almost certainly significantly better overall IQ for video (based on both processing and number of pixels), ...

So I'm not guessing anything. The thread is about video quality. Not about stills quality.

The X-H2 manages to shoot oversampled 4k without a crop. The X-T5 on the other hand has a 1.23x crop. This means that the heat sink is not sufficient for the 40mp sensor in video mode. Even if it had better heat dissipation than the X-T4 it wouldn't change a thing because the 40mp sensor is way more demanding compared to the 26mp one.

And again, this thread is about the video capability. CIPA rating is for photography only (how many photographs can be taken until the battery runs out).

Of course, if one can live with the additional crop factor, the image quality should be almost identical. But the crop factor means that for example the 16mm lens is going to behave like a 20mm one, the 23mm like a 28mm, etc.

And I don't quite understand why you're talking about 2k. 16:9 video is either 1080p, 4k or higher. Anything between doesn't make sense. And 4k is slowly but surely the new standard.

TL:dr
We're talking about video NOT photography. An oversampled 4k image is almost always sharper and cleaner than a subsampled image.

Oversampled 4k shot on the X-T4 is going to look better than subsampled 4k on the X-T5.

Oversampled 4k shot on the X-T4 is going to look similar compared to oversampled 4k on the X-T5 (with 1.23x crop).