Bitcoin approved and discovered in the world on 2009 and the first price is $0.
And this the history and bitcoin table when discovered in the world from 2009.[Using USD Rate 2017]
2009 [Discovered] - 1btc = $0
2010 - 1btc = $0.1 - $0.08
2011 - 1btc = $0.75
2012 - 1btc = $9.04
2013 - 1btc = $301.20
2014 - 1btc = $753.01
2015 - 1btc = $451.81
2016 - 1btc = $828.31
2017 - 1btc = $3664.25
From this list we know bitcoin is not stable , frequently make increase and reduction on price.
Is there a possibility of a decline in the price of the bitcoin future , in doing so we must make a choice better invest a bitcoin or not ?
Yes of course, anything is a possibility so the price reduction may occur in the future but if you take a closer look at the prices it still goes up no matter what, it is just that there is a reason why the price of bitcoin goes down in the year of 2014 to 2015 I think you know what happened.
Besides of the issues that bitcoin has faced off in the past it still bounce back and keep moving forward because many people still trust its future and only 3rd parties are the reasons to its fall down and not the bitcoin itself. No such thing is a short cut to the moon, we must embrace the step by step process in able to achieve what we want.