Bitcoins are fixed and can not be added. If demand grows, nothing will happen no matter what happens beyond the high bitcoin value. People can still own small quantities.

By the time the last bitcoin is produced, so many forks will appear, that most people will stop understand what bitcoin is.

21 million BTCs X N will be enough

No, high demand won't increase the supply of Bitcoin because like Gold, Bitcoin has a limited supply. High demand will only increase the monetary value of bitcoin and since bitcoin is subject to deflation as it is being widely used, it encourages hoarding and holding, much like what the most of bitcoin holders are doing.

Yes, Bitcoin supply will forever be 21 millions and It's enough.The actual supply after all the coins are minted will be a lot less, The total supply will be like ~17 millions.

like most comments in here i don't think that's possible the bitcoin supply cannot be expand unless they figure out otherwise which i dont think will happen

No it should not. Bitcoin is Bitcoin because of the limited supply and I guess that is more than enough for all of us. I cannot even earn or buy 1 BTC, Imagine that, 21,000,000 BTC and yet you are not able to acquire 1 BTC. Even if the demand goes higher, BTC will remain with the limited number of supply and I guess increasing it will damage the reputation of Bitcoin, Trust from the community will lessen and worst, it's price might crash real hard that no one will use it anymore.

The high demand of bitcoin will only make the price of bitcoin to be higher but cannot lead to the increment in quantity.

I think it is already been set the 21 million bitcoin that has been made wouldn't change even if the demand for bitcoin became so high,
I think that they couldn't add more than that because it was already been set from the start.

Of course it will not because the high demand in Bitcoin will soon result into price to skyrocket. In fact the supply will become scarce due to investors keep on holding their coins for long term investment. Whales are hoarding and most of the bitcoin community from early to late adoptors makes Bitcoin more valuable than today. I know that time will come 1 Satoshi can be equivalent of todays price of 1 BTC or even more like we can buy house and lot, cars or almost anything and that is because of the increasing trust by public and private companies, increasing Bitcoin community and greed investors. For me hard forks are just system upgrades and some kind of free coins or giveaway it will of course not change Bitcoin's supply.

21 million bitcoins limit would remain unchanged forever.But people would start using the word satoshi in future which represents 0.00000001 of 1 BTC.Bitcoins value is very high today reaching $14,160 and so,10,000 satoshis equals to $1.42 which would be a much affordable amount for even normal people to buy.

But there would be a great demand for whole bitcoins in future when all 21 million bitcoins supply gets completed.Bitcoin would be saved as a treasure at that time.