Many of us are hoarding more Bitcoins over time.
Indeed. And many also use it as currency too.
That is also the reason why Bitcoin dropped sharply on exchanges transactions in the past few years.
If you mean the
number of Bitcoins at exchanges, I'd start by blaming the rich ones - usually companies - for doing that.
Will we sell out of Bitcoin one day?
No. We will just keep all of them until we die, since we don't like nor want to enjoy life. (/s)
PS. Did it occur to you that people/companies buying Bitcoin actually buy from others who are... um... selling? And since price is still way under 1 billion a piece, it means that there are plenty of sellers?