The one area that few people in this particular debate topic focus on is the "left hand" of mining...

In mining, you need processing/calculating power, of course.  But that's not the full equation.  It's "how much power do we have" for "how much energy we put out."  The only reason ASICs are superior to GPU or even CPU mining is because of their speed PER kilowatt-hour.  You could theoretically have millions of CPUs still mining, but the power requirements make no financial sense.

The next step isn't about faster-than-ASIC, it's about less-power-than-ASIC.

I think instead of counting on faster and faster hashrates, you'll find more ASIC miners who switch to solar or wind energy for "free" energy.

To me, that will be where bitcoin mining finds its most profitable path -- no energy costs, high output.