If all the Bitcoin users refuse the spend their Bitcoin and decide to just hold all of them, then the price of Bitcoin will not move. Bitcoin's price will not increase, it will not decrease as well. No movement will be detected until somebody decides to sell their bitcoin or until somebody enters the bitcoin world and decide to invest some money into Bitcoin.
Obviously and that actually never happens because there are always people for selling or buying bitcoins because the community or the user database of bitcoin is too large so if someone holds his coins then someone else sells them because he needs money.
of course it wont happen in my opinion, bitcoin is a perfect currency and i doubt that people will one day just decide to not use it