I expect the Full Frame format to lose its popularity in the next 5-10 years for the following reasons:
Weight and size: A camera can be compared to a measuring device, the application of which to an experiment can alter the very experiment itself. The smaller and lighter the camera, the purer the reality it can capture. The principle of uncertainty is a pillar of modern sciences, and photographers should not ignore it. If we aim to capture more, we must use a smaller instrument.
Consider street photography, for example. A larger camera may attract unwanted attention, making it difficult to capture candid moments. With a heavy camera, you may be tired sooner and miss a perfect landscape photo - it is another example.
Bokeh: The growth in the quality of optics enables the production of lenses with larger apertures and higher resolution. A Full Frame format does not require more than an F1.8 aperture for practical object separation. The rest is a small niche. Autofocus lenses with an F0.9 on M43 (equivalent to F1.8 on Full Frame) will become mainstream for lens manufacturers in the next 5 years.
Sensor resolution and dynamic range: For the majority of photography and videography applications, the sensor should not provide better dynamic range and resolution than the human eye. In the next 5-10 years, we will likely have smaller sensors that can deliver such quality.
Therefore, I expect the bulky Full Frame cameras to disappear and be replaced with M43, 1-inch, and smaller formats in the future. This seems very obvious to me. Is it also obvious to you?