The price depends on supply and demand like everything.
As can be seen as so far the price of bitcoin has been strongly correlated on the nr of accounts that hold bitcoin.

The question is what will bitcoin ultimately be used for. Payments / Loans / Equity / Derivatives?
If its just payments it will be a part of a 90 trillion dollar supply
If it includes everything it will be a part of a several quadrillion dollar global market

There are many alternatives to bitcoin today but bitcoin is still the most widespread and distributed currency.
If it will remain this case looking at history we can expect 90% of the other coins to disappear.

Expect it to fly high if it stays the big gun.

https://www.marketwatch.com/story/this-is-how-much-money-exists-in-the-entire-world-in-one-chart-2015-12-18