Image models support merging already. There exists thousands of StableDiffusion models for that reason only. Downside is that almost all models you see are now inbred. Community does talk about it and can see the effect this is having on the image quality. A prominent example is you will see the exact same japanese kind of girl face from almost all models out there when you generate image of a woman. Check out Civitai to see what I am talking about. It's not easy to train new models but super easy to merge.

We can expect an explosion of LLMs using this technique similarly. And later at some point the degradation of quality perhaps. Or may be all those LLMs will be just saying the same things at that point.