Bitcoin will die if there will be no demand in the market and there is no people using bitcoin because the only source of stability of bitcoin market is its demand so if the market will lack of demand then that will be the reason for bitcoin to die and suffer a huge loss on the market but there is no possibility for bitcoin to experience that because the market is very active now.
Yes, it exists only because of the constant demand of users as well as any other crypto currency.
Do not worry about it, most of bitcoin users are trader, So bitcoin will always flowing. I agree that bitcoin will die if no one use it because we are who give this awesome and usefull thecnology a value as money. The number of bitcoin users are increasing so it will not be die.