I wouldn't say never, at least for C. elegans: there's been quite a bit of progress on imaging its brain, and it's plausible we'll have a fairly complete pictur

I wouldn't say never, at least for C. elegans: there's been quite a bit of progress on imaging its brain, and it's plausible we'll have a fairly complete picture in a few decades: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7801769/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7801769/ But the challenges are substantial, and these imaging techniques (mostly optical, not MRI/etc) depend on the simplicity of C. elegans: its brain is essentially a thin disk, with only 300 neurons in its entire nervous system, and it is surrounded by a transparent membrane. I am not sure how these techniques could possibly extend to something with a thick exoskeleton like Drosophila. And there are great difficulties keeping track of just the 300 neurons in a moving nematode with its own unique brain; it seems completely intractable with current tools to extend the complexity 50x, especially since fruit flies move far more rapidly and have far more individual variation.