Although it is unrealistic I was curious what would happen to bitcoins mining algorithm and hash rate.
As you said, I don't know how meaningful it is to comment on an unrealistic topic. At worst, however, the difficulty level is adjusted within the next 14 days and mining continues.
It's not changing based on a number of days but on the number of mined blocks (as mentioned above).
It'd be a hell of a time for other Bitcoin users as only 1 CPU has to do the job all the miners in the world were doing before, so it's going to take a long time before the set of another 2016 blocks is mined - which would indirectly rise the number of active miners as the Bitcoin network, my logical thinking tells me, would get clogged.. resulting in our transactions being stuck, so Bitcoin becoming unusable until difficulty gets adjusted.
If Bitcoin ever reaches the point where only 1 CPU in this entire world is mining, I think there are way more things we have to be concerned about!
Wouldn't the network be exposed to 51% attacks as soon as the difficulty is adjusted? Wouldn't only 1 miner in the world mean nobody cares about BTC anymore (or you're living in a post-apocalyptic scenario)?