It's a matter of time that btc and other currencies will bounce back again especially if you are going to check the market as the prices are starting to move upward now from it's hard crash. If there will be no dump again then it was the bottom as -50% is a hard dump.

But traders know how follow the flow of the market, I am pretty many of them have cut their losses and recover their profit by buying again after the hard dump that happened. Guaranteed investment will only occur if you are planning to hold for a long term one especially that btc will not lost it's value easily as it will surely bounce back right after the crash.