Yesterday, the FCC published details on a new Apple TV that appeared to be smaller than the current Apple TV third generation. This information led to widespread speculation that a new model of Apple TV was about to arrive with new features too. Unfortunately it appears that this is not the case, the dimensions will remain the same but the internal components will be subject to just minor changes. The Verge managed to get a statement from Apple to explain the confusion.
We sometimes make component changes which require an updated model number for regulatory approval. The component changes we made don't affect product features and Apple TV customers will continue to have the same great user experience.
It had been rumored that the internal component change could be the addition of the A5x processor; before we will know if this is the case, we will have to wait for someone to crack one open and take a look inside as Apple is not giving out any more details. Either way, the experience and look of this updated Apple TV will be exactly the same as it was before.
Source: The Verge