So the confirmation speed may decrease if people do turn miners off and others do not tun miners on to make it more profitable?
No, the difficulty adjusts every 2016 blocks so that confirmations will always average about 10 minutes.
Sure, but since a retarget just happened, if 50% of miners shut down right now, blocks would slow down for the next 2008 blocks
Was there 50% less mining power 3 months ago? No, there wasn't.
25*350$ = 8750$ and 12.5*640$ = 8000$ so miners are making almost the same they made 3 month ago so I don't see why they would start shutting don now...
I suppose that could be true too!
The mining difficulty, though, plays a large part in this! It hasn't actually inceased by very much though since then. But if it were to increase by around 5-10% there would be a massive effect on the sustainability of the machines in use!