The rarer it is, while holding value, the greater it's value will become. It won't take long for the rareness of Bitcoin to become evident, especially when there are more people who want it.
Remember one important thing. The closer we approach the 21 million maximum, the slower new ones will be created - half as many this 4 years as the last 4 years. Yet, if there isn't something that drastically reduces the population on earth, there will always be way more people who want it than the number of bitcoins out there. And the number of people will be increasing.
As long as something doesn't destroy Bitcoin's ability to be used, it will continue to increase in value. Odds are that, as the number of people using it increases at a faster exponential rate than the number of bitcoins being created, the value will only rise.
The thing that will make the value of a bitcoin shoot beyond the moon, will be when the effect of all those $17 trillion dollars that were created in various Quantum Easing programs starts to be felt. This will happen as this fiat is gradually dumped on the market.
Lots of stuff to consider.
