I think everything is possible, now with 1 wallet etherium we could save a lot of altcoin and of course dev. etherium would do the best strategy to be number 1.
I don't think "one wallet to store them all" is actually a good idea because the thief only have to find one Private key to hack everything from you. Also, there are exchanges out there that holds most of the altcoins, even the ones that doesn't have an ETH contract.
I think that Eth actually stand a chance against bitcoins, at least to reach a competitive level if not surpass bitcoins. Because new altcoins are using ETH contract. That serves as an advertisement to both coins. The new altcoin rides with the popularity of ETH and ETH gets new investors because of the people that have seen the advertisement of the new altcoin.
Correct even when you use fiat is not recommended that you use a single bank account for everything, you need to have several so you perform different actions with them and in that way if one is compromised then you dont lose all your money and the same applies to bitcoin or any other coin.