What if mining does become the main source of income, do I still need to file for taxes?
That solely depend on the laws regarding income, taxes and Crypto in your country. In Canada, its not legal tender, so i have to declare capital gains regarding it. For instance if i buy 100 Bitcoin over the course of a year for 40000 and sell for a total of 40500$ then i have a 500$ that i should declare as an "Other Income".