I think that bitcoin will last forever, it's because this is the next big thing in the world.
I think soon that all of the wealthiest people on earth will be replaced by the people who invest and start saving altcoins and bitcoins for the future.
If you observe carefully you will see the progress of the value of bitcoin in the market. You will see the growing rate of each altcoins as well as bitcoins.
In my own opinion bitcoin will never end this maybe the next source income of some people even rich people are also investing in some crypto currencies.