It's the software. You're restricted on Android or ChromeOS. Unless you have all your data in the cloud which is impractical for bigger files. Same goes for file management, some people still like to have control over their music and photo library locally. Yes this could work in the future, I don't think the infrastructure is there yet, at least not for the rest of the world (see my previous post).
I'm not saying it can replace the Mini or another computer today, but the question was if this "is the new Mini [of] the future?" Hopefully my next comment will explain better.
I'm still not with you on this one, sorry.
I'll explain...
Why not just buy and use the $35 Raspberry Pi instead?
Certainly.
Sorry for the late reply, but better late than never, right?
Now, let me ask you guys: what is the difference between a monitor and an iMac? Not much besides some laptop hardware in it, right? What's the difference between the Mac Mini + Monitor vs. iMac? Technically nothing, besides the fact that one comes packaged as an all-in-one unit and the other relies on the monitor as a peripheral.
Well, why couldn't an HDMI dongle computer (like the Chromecast) BE that computer? Don't get hung up on the OS it's running... pretend it's iOS or even OS X compiled to run ARM hardware.
Computer components keep getting smaller, more powerful and cheaper. So can this be the mini of the future? Sure, why not. It's here today, just not as powerful as the Mac Mini. The mini of 5-years from now will look nothing like the Mini we have today.
Think about it like this: last year's Cortex A15 is faster than a Celeron processor in many respects. Just to give an indication of how x86 stacks up against ARM. With the rate of development in ARM architecture (compared to x86) - despite Haswell - do you really believe that in the next 5 years we couldn't have an HDMI stick be a "Mini" PC while the current Mini form factor would now be your server? Look at the size of the new Mac Pro.
I hope that more eloquently explains my position and why I said what I said.