There exists a square-cube law (or something similar) so that computation becomes less and less efficient or precise or engineerable as the size of the computer or the data it processes increases, so that a hard takeoff is impossible or takes very long such that growth isn't perceived as "explosive" growth. Thus, if and when strong AI is developed, it doesn't go FOOM, and things change slowly enough that humans don't notice anything.
If Strong AI turns out to not be possible, what are our best expectations today as to why?
I'm thinking of trying myself at writing a sci-fi story, do you think exploring this idea has positive utility? I'm not sure myself: it looks like the idea that intelligence explosion is a possibility could use more public exposure, as it is.
I wanted to include a popular meme image macro here, but decided against it. I can't help it: every time I think "what if", I think of this guy.