AFAIK, there will be a time when there won't be anymore Bitcoin to mine, but I don't think there will ever be a time when we won't see any Bitcoin to buy. You have to understand that Bitcoin isn't just in a single unit like 1btc, 2btc, 3btc, and so on. And I guess that is literally one of the reasons why it is divisible into sats. So, no matter how expensive a single BTC gets, its sats will still be affordable for everyone to buy. Bitcoin will always be available for everyone, even if a sat cost $1 or more.

People will always sell at some point. That's what drives the market. You have to sell for me to buy, and the reverse can also happen. Mining will definitely come to an end according how it was designed, but i don't think the same will ever happen for supply due to its divisibility.