when all miner stoping his mining hardware due not profitable anymore because the POW is ended, and no people interesting to stake it.. 
1.Why would miners stop mining ?2.People are waiting in a long que to take their places if given an opportunity!
3.The difficulty will increase eventually but there will always a group of miners who would still manage to taste the cherry on the cake!
4.Argument is invalid,bitcoins live forever!
this case will be happen if miner not have chance to take ROI in more than 2year, or maybe the electric fee higher than mining reward, if you are home mining, you will know the hard to calculate each cost of mining.
why should it even die?
there is no reason for that. bitcoin is strong and also it is being developed so even if something happens it can change and adapt itself with the new world to support the changes.
bitcoin is currently far from dead, bitcoin still have good growth for the next several decades and still have a great opportunity to become bigger in the future. but when bitcoin depleted mined some speculation about bitcoin will appear dead. due to the impact of the miners, if nothing is the miner. we will not get delivery confirmation. so that everyone would be stuck.
