The most challenging thing will be:

When the privatekeys of the lost coins with no owners - 'shalecoins'  https://bitcointalk.org/index.php?topic=5134441.0 - will be 'fracked'.
The first group will then sell all these coins because they will then know that it is possible to get the privatekeys and that others could 'frack' them. No matter what the BTC price, they will sell them.

There are more than 1,000,000 'shalecoins' with a 10+ billion US$ value. So we can expect that there are private groups who want/try to build a supercomputer.


https://bitcointalk.org/index.php?topic=5166180.0