What I want are:
1. Native support of bitrates outside of 48khz. Not just hi rez, but CD format (16/44.1) for lossless bit-perfect streaming of Redbook CD quality would be nice.
2. App store - Obviously, it would need to be full featured and have apps like Plex, Amazon, Lynda, and Vudu.
3. 4k - I would love to see this since this is where things are headed, especially, since they make seldom hardware changes to the AppleTV.
4. Siri control - I want to be able to control all of the features right from Siri, preferably with an option for an always on mic (like Amazon Echo), but I would settle for Siri iPhone control.
5. More support for different codecs - I wouldn't need Plex if iTunes/AppleTV supported more formats.
6. Multi-room Airplay features - Right now, you can select to send the audio to one Airplay device. I would prefer if I could send it to any or all devices like iTunes and still have the ability to play directly from the AppleTV, simultaneously.
7. Direct streaming from the web, similar to Chromecast - I should be able to start a program or album from my iPhone, send it to the AppleTV, and then turn the iPhone off.
8. Remote - I want the box to continue to support IR. I don't want another PS3 situation where I have to have an adapter or a Bluetooth remote sitting around because I can't use my Harmony remote with it.
9. I want an Ethernet port like we have now and a separate optical output like we have now. It means I don't have to rely on wifi and I can use the AppleTV in an audio only setup later.
10. I think it needs a video camera for homekit features and facetime.
11. I still want Airplay and Airplay mirroring and many of the apps we have now (Podcasts, iTunes, etc..). However, AppleMusic should be available.
In a perfect world, I would also love to see an Apple branded home theater receiver with full Siri/voic control, Homekit, and AppleTV/Airplay features. However, I don't see that happening.
Did I miss anything you want to see? Leave a comment or send me an email with your suggestions.