Increasing demand of bitcoin will trigger a tremendous increase in its price. Since more and more people go after it, sellers will have a good time enjoying bigger profits from selling bitcoin.
If you have bought bitcoin at dips then selling it at a high price will definitely earn you a lot of money. Imagine how much you will gain if you bought it at $1K and the price goes to $50K this year. You will become instant millionaires. That's why its really better to hodl on bitcoin for longer terms.
As far as the consequences of increasing demand, bitcoin will grow exponentially but there will be serious issues on high transaction fees. I think we can't get out of that situation, as long as bitcoin growing, transaction fees will increase as well. It's going to be included as package. That's one of the drawback that I'm seeing that may happen in the future.