If I am not wrong what you mean is bitcoin demand decrease? Anyway if it decrease you can't either sell away what you have currently or hold it if you have no need for the money. I believe it will still have demand in the long term.
Maybe i will suppose that the decrease mention here is decreasing in value or decreasing by demand. So if bitcoin value decrease then its not time to panic as a crypto currency volatility is always normal and it is an instinct of every business minded individual to buy those important asset while still at low price to sell it someday when its price back to high to double or triple its profit. In other side if more people doesn't believe anymore in bitcoin then the tendency is they will sell there bitcoin and the supply will increase causing its value to dive at very low.