Only would happen if the every single one of us who holds bitcoin decided to stop selling all of a sudden. Whales could hoard all they want but if they all at a point started to control bitcoin for their own greedy causes, people could simply call it a day and move on to a different cryptocurrency, pulling all of their holdings out and find another decentralized cryptocurrency in the market that they can invest on. If you're scared that whales are becoming powerful by the day in the world of cryptocurrency, do not fret because the most powerful component of this system is us investors, we get to decide when bitcoin is valuable and when it would be dirt cheap, literally.
Bitcoin is limited in quantity. News like so and so billionaire or so and so company bought 100,000 BTCs is now commonplace due to the dip. Will there be a time when there will be no bitcoin to buy. If so then what will happen then?
I don’t think it is possible that such thing is going to happen. You know that there are lots of bitcoins circulating and people are making use of it for transaction every day, so I don’t think there will be a time where we run out of bitcoins to buy or use. As these big private investors and institutions continues to invest their money in Bitcoin and buying Bitcoin in huge amounts, the price of Bitcoin is going to continue to increase in value and then it’s price in Satoshi will continue to also increase in value (that's the fraction of Bitcoin). And as this continues, that means there will be more available for people to buy, although I do understand that everybody wants to own one Bitcoin , but it is not a must that you will own one Bitcoin, because you can buy in fractions.
I guess this is just a worst case scenario brain exercise? Since no matter what happens there will always be a person who would want to sell their coin for profit, especially if in OP's situation all whales hoard the coin, which will pump the price of bitcoin dramatically forcing other people who have their coins on holding to sell it and take the profits. So no matter how we look at it, the ones that will be at a loss will always be the whales, because in order to win they had to follow the delicate balance of the market where they can only acquire a definite amount of crypto before the people decide to sell it.