As long as mining is profitable and the costs are reasonable, if we keep going like this then it wont last for another 8 years, imagine how many miners will be needed to mine by the next 2 halving? would you buy 100 ASICs to mine half a Bitcoin in a week?
Mining could maintain profitable or not. But the lasting time of bitcoin is not directly dependent on mining. The usage and demand are much more important.
I think this question is now more important and significant as how long will bitcoin will last in its original form or are we splitting it up making two chains and creating a whole lot of confusions. I hope soft fork is activated and there is no two chains of bitcoins. If this happens bitcoin price will rise to nearly the double, making it good for everyone.