How many image formats CAN'T you read today that you could read 50 years ago?
2) Images are much much much more ubiquitous than book formats
I would bet that the vast majority if not all image formats that can't be read anymore are due to their spec never being published.
GIF, JPEG, MP3... these are all patented technologies whose patents have expired into the public domain. That they're still used and useful today is a very strong indication that they'll be available in another 50 years. I think that having public patents for image and audio formats helps to demonstrate that it's more than just survivorship bias.
I don’t know. How many?
That supports 200 image file formats as inputs, and you can then export it to PNG or GIF or BMP.
Your question, on its face, seems ok, but really, there's probably millions of image file formats lost to the sands of time. Shareware image creation programs, tiny fly-by-nite company's software that only ever had one major release (probably some cad formats in there. Those were where i used to always have problems 22 years ago when i did this for work.)
however, at least 200 of them are preserved through that "company's" dedication to this topic.
You don't need binary compatibility. You can load a gif on any computer today, and it's old. I can view aiff image files from my Amiga still.
We're already 50 years in on many formats.
Where it becomes uncertain, it DRM laden, closed source applications with bespoke file formats.