For 2nd point, "Bitcoin will wither", I do not see in your post the reasonable explanation on that. In my opinion BTC will still be there, simply its first and foremost crypto currency in the world, never underestimate the pioneer. BTC is potential to become world's store of value asset due to its big value and solely usage of bitcoin blockchain( to serve BTC transfer transaction only). Ethereum and other cryptos can be useful for other purposes due to its blockchain flexibility(smart contract and other technology to build dapps on top of the blockchain), but its also the flaw because noone wants to use those blockchains to build end-user platform with billion transactions if those crypto currencies value is too high (that implies high fee when running transaction on blockchain). But lets imagine, with 1BTC = 1M$, you can easily make 1B$ transaction with very low fee in compare to using bank system instead, and the receiver can get that amount of money in the same day (in this case I do not count on bitcoin blockchain scalability project like Lightning network to make your transaction happen instantly ). After all, future has room for all of us.
The idea is that it will be supplanted by other crypto. It's happening already, if you look at btc % of crypto market cap