Oh that could do it! That could be the big cool feature that makes Apple TV different - unify the various streaming services with one searchable interface.
Wouldn't be all that useful for me since I only need Netflix, but if it also worked in streaming files from a PC or Mac, or Apple devices connected to the same network that would make me get one.
I hate to tell you this, but this has been a standard feature of the Roku for at least 2-3 years. It's right there on the home screen, under the channel list. It searches every provider who agrees to give access to their content database for pricing/availability/metadata. That means Netflix, Amazon Prime, Hulu, RedBox, Google Play, Crackle, etc. All of the bigger names.
Apple's version will have at most, the same providers, plus Apple's own store. But, they probably won't have Amazon or Crackle or any service that allows renting or buying content, since Apple demands a 30% cut of anything purchased through that app, and at the same time demands equal retail price points.
So on a Roku, Amazon can sell a movie with 1 click for $9.99 and put it in your Amazon content library, permanently. They take all $9.99 of it, and give some to the rights holder, as required by their own contracts. If they put an app on the Apple TV, they could only charge $9.99 for the same movie, and would have to pay the same amount to the rights holder, but also give $3 to Apple, just because. You can assume that there is a 50% markup, or less. That means Amazon takes $5 when they sell a movie on a Roku, or on their own site. That pays for their CDN expenses, storage, streaming, content management, metadata tagging (have you seen their in-content tagging? It's dynamic and interactive and really quite cool), and includes whatever profit they make. If they sell the same movie through an AppleTV, their baseline drops from $5 to $2, and they still have to do all the same work, and pay all of the same distribution costs. All they gain is Apple TV viewers, which let's face it, isn't that much of an audience. It would only ever be viable for Amazon-exclusive content.