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Bitcoin can make a lot of people rich, you know that bitcoin's existence, sustainability and main nature is to increase over time. Not only does bitcoin create one-time opportunities where you can buy and hold it as part of a $40k investment process, bitcoin doesn't make you rich quick, it boosts your awareness of yourself. and education about financial management. from there you have more opportunities to get rich.
I don't refuse what you have said about bitcoin but here, op wanted to know only one currency name that would make him billionaire by grow his capital. I agreed on the point of bitcoin made people riches even Millionaires & will keep making in future but dont think it is possible for bitcoin to make 1 Billion dollar from 40k$ only. But that doesn't mean i suggest to avoid bitcoin. So my humble request to be logical
Aiming to be a billionaire status in just mere 5 years by investing cryptocurrencies with just $40k worth of investment is quite impossible to do. Even if the OP will pour all of his available funds towards bitcoin alone, that aforementioned aim is not really achievable within the given time frame. Being a millionaire sounds possible and realistic but billionaire? I really don't think so.
As for the OP's question which altcoin is going to give him profits in 5 years except btc and eth, my choice would be BNB and SOL.