I think your second point is pretty contestable. Sure, png was a direct response to the gif/lzw debacle, but it is equally probable that someone would have said

I think your second point is pretty contestable. Sure, png was a direct response to the gif/lzw debacle, but it is equally probable that someone would have said "you know, we could probably do better". For example, JSON didn't arise from the XML patents (of which there are none), it came from someone saying, "Seriously we all know this thing we're doing with XML could be better", and doing it. Same for a lot of programming languages. Same for a lot of things. Technology seems to progress by a combination of people's interest and snagging at the low-hanging fruit of "this has become unbearable". At some point, a better gif would have happened just because it hit the proper pain point.