The future of Bitcoin is still hazy. Bitcoin and cryptocurrency in general is still in the early stages of development as is far from global use let alone mass adoption. For this reason it's almost impossible to put an official value on a Bitcoin unit for the future but as with all inventions and technologies there will always be projected values and predictions.
In the scenario that Bitcoin replaces fiat currency in the future then the 21 million available supply would share the world's GDP. If we say the world's GDP is $80 trillion then each Bitcoin would be worth roughly $3.8 million. Of course it is extremely unlikely that Bitcoin will be the only digital coin if cryptocurrency is adopted by the masses so these are all a bunch of 'ifs' and wild predictions.
It's extremely likely that different countries or factions will utilize blockchain technology and start creating their own form of cryptocurrency in the future to rid of physical cash. Although money will still be controlled by a central party and the government, this is a necessary step in order for the general public to accept this form of money and trust it works. Eventually, when everyone is using some form of digital cash, they will see the benefits of a decentralized system vs a bank and move over to the Bitcoin network.
Although many still have no idea what Bitcoin is, the majority who reside in the world of tech know about it and some even use it on a daily basis. Public figures inevitably love to make predictions on hot topics within this realm. John McAfee (founder of McAfee Associates) has boldly stated that Bitcoin will reach $500,000 in the near future and famously added over Twitter that "if not, I will eat my dick on national television".
Rick Falkvinge, tech entrepreneur and founder of Swedish Pirate Party, makes his prediction that Bitcoin will eventually capture between 1-10% of the global forex market which values each Bitcoin between $100,000-$1,000,000.
Wences Casares, CEO of Xapo, states in an interview that his predictions were that in 10 years each Bitcoin will be valued between $500,000-$1,000,000.
There are dozens of Bitcoin price predictions floating around the web but the truth is that no one can know for definite because there are many factors that need to be in place for it to hit certain numbers such as mass adoption. However, one thing that the majority of cryptocurrency experts believe in is that the Bitcoin price forecast is an upwards trend.