"We will have a true AI in 50 years" is a time-invariant statement. And yes, I've done AI stuff as well, and am now a social scientist, so I mix the two freely. We are at least five orders of magnitude from having the same computing power density as the human brain.
Actually, arguably, we are infinite orders of magnitude away from the same power. As the previous poster pointed out, the human brain is actually an exceedingly complex analog computer; thus it has infinite possible states, and since our computing power is not currently infinite, QED.
Also, the brain is not deterministic. So not only is it not digital, it's also a non-deterministic analog computer. It's going to be a long, long, long time before we get anywhere within shouting distance of its actual power. Unless P=NP, which is seeming less and less likely (and it never was very likely) as time goes on.