Hoping to have about 10 BTC a year from now. Best case scenario is that those 10 BTC will help me to seriously cut down on work hours in 10-15 years time.
It will happen.
It will happen when you dont sell your bitcoins in 3 years at 20.000 Dollar

But i bet 99% will do this, i will wait from now to 2021 and see what will happen,
because with 20.000 Dollar per bitcoin i can not go in retire.

If it was for sure that bitcoin would be worth 20000 USD, everybody would now buy enough btc to retire

At 20000 USD it is definately possible to retire, as long as you hoard enough.