I absolutely agree... Bitcoin price will be 70k end of 2018.
There is a possibility that bitcoin price can be high for ever because still there are a lot countries are waiting for it and in next year Im sure that bitcoin will arrived to many countries and this process will be continue until unless its not reached to all countries and once if it reached to all countries so its price will go more high and will become stable.
Yes I think this is possible because the price of bitcoin is always unstable and changes rapidly, we see that the price of bitcoin decreases after the it reaches to $11,000 and now it is about $ 19000 @means that price changes i am hopeful that bitcoin price will continue for a long long time, because bitcoin still has avery good potential to increase its price.