When it comes to making a concrete investment plan, conducting thorough research is crucial. While BTC and ETH are widely considered secure options, other altcoins have demonstrated reliability over time. However, it's important to note that the cryptocurrency market is highly volatile, and predicting the future performance of any specific coin is challenging.

As for your question about investing $40,000 in a cryptocurrency that could potentially make you a billionaire, it's essential to approach such speculative investments with caution. It's difficult to predict which specific coin will yield such enormous returns in the future.

To make an informed decision, I recommend considering factors such as the project's fundamentals, team expertise, market demand, adoption potential, and technology innovation. It's also advisable to diversify your investment portfolio to mitigate risks.

Consulting with a financial advisor or conducting further research on promising altcoins can provide you with additional insights to make an informed investment decision aligned with your goals and risk tolerance.