Is Ethereum and other altcoins taking over and replacing Bitcoin?
If so, how fast will this happen?
Replacing Bitcoin about what? If it is about payments, there are already altcoins that outperform BTC in tx/sec, fees, etc.
People currently only use BTC as a store of value or investment. So if it's about price (market cap), BTC will still be #1 until there is a new technology that fundamentally different from this "blockchain technology" and solves "the trilemma."