If the price of the Altcoin goes up, then the Bitcoin value will go up. The reason is that when the price of Bitcoin goes up, the price of Altcoin goes up as well.
If people start buying Altcoin more than today, the price of Bitcoin will go up as well.
If the price of Bitcoin goes up by 2021, it will be a record.
Am I right?
Firstly, there is no such thing anyway. If 5 are invested in altcoins, at least 10 are invested in Bitcoin. Secondly, let us assume that the situation has developed as you think, but this time the result will not be so. Because trader sells Bitcoin for getting altcoin. In this case, Bitcoin does not increase, on the contrary, its price decreases.
It's not, when you are watching so many thread here that was asking about how to build the portfolios and the majority of them will try to pick bitcoin as the main choose to be filled with a lot of their money and then they will put the rest of their money into the altcoin.
I can assume if there are 10 people who interested investing on crypto and they are all will be investing in bitcoin and altcoin. There was a small chance for some people may only investing on bitcoin.