Every affair in the dark web will use Bitcoin as a method of payment. In the dark web there are various illegal businesses such as the sale of illegal firearms, drug trafficking, assassins and hackers.
no it won't.
there is always going to be some usages in dark web or any shady and illagal activity, and that is like any other currency that you can thing of, USD, EUR, CNY,...
but it is no longer 2009-2011 that people think bitcoin is anonymous or is their only option. right now there are anonymous coins that have all the attention from these criminals and they are using those anon coins such as Monero in dark web instead of the easily-traceable-bitcoin.