Does bitcoin value will increase in the future if more people decide to use it?
Lack of any centralization (Central Bank) makes bitcoin Heavily affected by the change in supply and demand law.
if more people decide to use bitcoin (More Demand) with the limited number of bitcoin "Scarcity"(less than 21 Million), the price will rise sharply.
The main factor determining the currency value is Encourage individuals to buy currency With the possibility of conversion to basic currencies easily.
All of these factors make the value of Bitcoin increasing in the future.
Even if bitcoin does not have a central bank we have a defined emission rate in the form of block generation and the block reward which is similar to what central banks do, the biggest issue as you have pointed out is the limited supply and the deflation, while this makes bitcoin extremely valuable at the same time people treat bitcoin more as a collectible than as a currency, this limits the supply even further creating greater volatility.