People think that Bitcoin will be valued more in the future. So they are both mining and buying bitcoin.
Is there any possibility of a decrease in demand for Bitcoin? Whatever happens, people give up using bitcoin.
Of course it is possible. As much as it is possible that the demand can grow high, the opposite can also happen.
A few reasons that can effect this are:
1. Bitcoin fails to scale
2. Bitcoin is banned from your country
3. Increased confirmation time
4. A better alt coin emerges that overshadows bitcoin.
5. A major bug is suddenly found on bitcoin codes
There can be more reasons that can bring the demand down that I have not thought.
I am really sorry but you are completely mistaken;
1. Bitcoin will succeed to scale with either the one or the other way. Nobody and especially miners want people give up bitcoin because they have spent millions of dollars in mining pools.
2. So what? Bitcoin uses internet and anybody can use it to buy things from Internet. Moreover banning has the opposite results from the intended ones
https://news.bitcoin.com/needham-banning-not-prevent-bitcoin-adoption/3. There is lightning network in alpha release for micro payments
4. May post the traits this alt coin so as it will overshadows bitcoin? or what kind of features bitcoin lacks from this super alt coin?
5. Wow!! After 8 years nobody found this 'bug' and 'major' one? If anyone find something like that banks will put him on their payroll without doing anything.
Today I read that Pakistan the 7th most populous country in the world may be the next major user after India
https://news.bitcoin.com/pakistan-set-to-become-a-major-bitcoin-hub/Yeah he was right and you were wrong! All of the things he mentioned are potential problems that could reduce the demand for Bitcoin.
Your answer for 1 hasn't happened yet, and didn't happen when the network was being clogged by spam transactions.
If Bitcoin is banned, demand will fall. A better Alt could overtake Bitcoin by being adopted by major companies and banks. ETH got to about 10% of the value of Bitcoin not long ago, a good new Alt could overtake Bitcoin.
That is ignoring a 51% attack and quantum computing. Both could badly hurt Bitcoin, reducing the demand greatly.