Stunningly complicated is an understatement
There is so much different stuff out there, that I'm convinced the average consumer (who probably does not take time to digest the wealth of research put into these forums) really has almost no clue about what they are buying. And, since the vast majority of "full service" dealers have gone the way of big box stores, help at point of purchase is virtually non-existent.
I was fortunate to have the information in this (and many other) thread to help me when I upgraded my 15 year old Sony (and I use the term loosely) AVR.
The point is... when looking at things umbrellaed by a term "future proof", my reasoning was that, like many, I would not be replacing my AVR for many years, given the last one is still ticking after 15 years. So, I was looking to find an AVR that would take me through those years, and keep me as current as possible with most/all of the mainstream improvements that would birth during the life of the AVR.
Oh, yea... and I while I guess I could lay out $5K for an AVR, I chose not to. So, after digesting all this information, and putting it into a price/performance equation, I ended up getting a Denon 2807.
I am confident that was money well invested in a "future proof" AVR, by definition of this thread. And, that it would provide me with many years of service, with upcoming changes in technology.
To me, that is what this thread is all about.
I'm sure others could go through the same process, and come up with another answer, other than Denon 2807. And, that would be just fine. The point is, if you digest the information here, you've made an educated decision. Make/model beyond that is preference.
Post #1 in this thread establishes fundamental guidelines. One can only hope we don't need to granularize it down to the n-th degree. I, for one, understand that nothing is truly future proof.