now a lot of investors are investing in bitcoin, therefore bitcoin has increased very rapidly, if bitcoin decreased what should be done?, whether the investors will lose? 
I'll avoid to losing my money, i'll wait until the time that bitcoin's value grows or increase again.
The investors will only lose if they will sell under the buying rate they got in. But if the price starts to decrease, i think they will just let their bitcoins stay for awhile then there's nothing gonna happen if they'll wait for it to rise up again.