The movement of chain will stop.  Automatically all transaction will be unconfirmed.  The Bitcoin economy will be in chaos.  This will result to fear and the buy support will start to be pulled out.  And then one by one cpu will start mining it again but due to global low hashrate, this will be susceptible to double spending.  But then all those who are holding BTC will make sure this wont happen so they will start mining it by themselves and the domino effect follows.  Basically mining Bitcoin wont end even if all coins are mined.  This is one of the reason, personal interest and investment security.  So be calm and hold your BTC for as long you want.