Now the mainstream currency, BTC-ETH, has the upper hand, and they have the strength and technology, but the future is likely to be a new project to replace them more mature and more comprehensive. What do you think it would be?
BTC and ETH are mainstream currencies? You're thinking ahead mate
If ever or whenever cryptocurrency goes mainstream then BTC and ETH will definitely take the lead. However, we are all open for possibilities and there might be a new cryptocurrency that will exist and overtake the lead. This is a little foggy at the moment but who knows.