I think this is the direction they are heading in. Like Coinbase and Bitstamp, they realized that gaining a foothold in the altcoin markets during this early stage is simply too important to neglect. Like Bitcoin, the time-tested and liquid coins like ETH and LTC will be sticking around for a long time. So, I imagine that this ETH rollout has been many months in the making.
It makes sense from that perspective that it would take months for them to roll out BCH, too. At their scale, supporting a major coin is no small endeavor. In time, I'm sure they'll be one of the go-to web wallets for LTC as well.
but there is still a huge difference!
services like coinbase are not just wallets, they are like banks. you give up control over your funds and they can use it as they like. for example they can use the bitcoin you deposit to trade themselves on other markets (just like a bank).
also they offer other stuff such as trading these altcoins which they make money from the fees.
blockchain.info doesn't do any of these!
they don't control the private keys so they don't have access to the funds you deposit.
they don't get any fees either for the services they provide.
this rises the question: what is the foothold they are trying to gain?
blockchain.info does offer "trading" in a sense. you can buy and sell BTC (and now it seems ETH as well) through their wallet.
they may not control your private keys, but that doesn't mean using them as a wallet is secure. you don't control the software pushing your transactions, which means you could lose coins in MITM attacks. you are trusting that the service isn't compromised.
the foothold they are trying to gain is market share for wallet usage, which translates to industry relevance. you can see that they are transitioning into the consulting space in an attempt to capitalize on this:
Just as we've done for millions of individuals with our personal wallet, Blockchain empowers global institutions with the same control, security and ease of use—and fundamentally changes the way they do business.