In https://github.com/ethereum/mist/releases 0.3.6 the files are named Mist. Starting in 0.3.7 the files are named Ethereum-Wallet.
Will files named Mist take over in the future, or will there be 2 separate files Mist and Ethereum-Wallet?
Mist is the browser for decentralized web apps. What Mozilla Firefox or Google Chrome are for the Web 2.0, the Mist Browser will be for the Web 3.0 (which will be decentralized).
Mist is still in heavy development (for instance it's not recommended to visit untrusted DApps until the full security audit is done). You can find the releases to date here. The current release allows you to open any Ethereum DApp with the Mist Browser (with the disclaimer above).
All other releases of 'Mist' are no Mist releases at all, but a bundle of Mist Browser with a single DApp: The Ethereum Wallet, also known as the Meteor DApp Wallet.
These releases are therefore called Ethereum Wallet as it only offers a bundle of the Mist browser with a single DApp: the wallet.
The future, with Metropolis release, will provide a full Mist Browser able to open any DApp available out there. The Ethereum wallet will only be one among them.
Let me first explain Mist in simple terms. There are two types of mist for Ethereum, one is a cryptocurrency wallet and the other is a browser.
Mist wallet is basically used to store and send your Ether. If you are choosing to buy, invest or trade in Ethereum, then you'll require a wallet to carry out the transactions. that's where mist wallet is helpful.
Mist browser, on the other hand, is a browser to access the DAPPS. Just similar to chrome and safari. But, with mist, you can access DAPPS and web 3.0.
Mist wallet runs on your computer, meaning you'll require it to download and run it from your computer, whereas Ethereum wallet is an online wallet where you'll need to access the internet and log-in to your wallet and carry out the transactions.
For more details you can read this guide: The complete Mist Wallet guide.