[gibybo]

>even the next generation of ASIC mining hardware (which will continue the exponential growth of worldwide hashing power) would require hundred or thousands of years (I don't know the specifics and can't be bothered to find the numbers with specificity), on average, to find a specific hash.

It would take much longer than that.

The current hashing power of the entire Bitcoin network is ~5 PH/s. If we assume it will increase 200x over the next generation of ASICs (this is unlikely), it will still only be ~1 EH/s. That's 1e18 hashes per second, or 3e25 hashes per year. Finding an input that hashes to a specific 2^256 bit hash would take, on average, 2e51 years. The universe is only 14e9 years old.