Every four years the amount of Bitcoin that can be mined halves. 2020 there will be another halving around about May. This generally doesn't increase an immediate spike, sometimes even a slight pull back, but then it lifts off. One major factor for me regarding the legitimacy of Bitcoin is who accepts it as payment. APMEX is probably the biggest gold and silver bullion dealer in the world and they accept Bitcoin for gold and silver.
Interesting. I see the price has been fairly stable for a while now, so this could cause a growth in the value.