Backwards compatibility has a lot of utility IMO, forward compatibility for me anyways is less important. What MS is doing with BC makes it much tougher for someone to justify abandoning the XBOX platform for competitors. How much the feature actually gets used is another matter but for me, I can say if I had known in the 360/PS3 era much of the titles I wanted to play were going to work on future MS consoles I would have invested more of my purchases on Microsoft's platform.
It's possible Sony offers decent backward compatibility for PS4 titles once PS5 is released but I honestly doubt they really thought that far ahead and may want to try and resell much of that software as they've already done with PS4 and earlier PlayStation titles.
I'm also curious about possible bottlenecks forward compatibility might introduce with future titles. Would enemy AI or numbers be compromised? What about level size, the amount of streaming of assets in and to some degree compromising immersion due to loading might be introduced?
Just looking at PC as a historical for this type of behaviour, it doesn't seem to be really any different. The developers set a goal in mind, that becomes the target spec and the the game runs on said spec.
Usually the spec chosen will be based upon the largest marketshare in terms of configurations (so RAM, CPU, GPU and GPU RAM), they'll figure out their min/recommended and go from there.
That being said, for X1 and Scorpio, all they need is the go ahead from MS that they are allowed to spec for Scorpio. But you wouldn't want to spec for Scorpio, unless its audience was larger than X1. I think from a business decision, when MS sees the audience has moved beyond X1, they will let developers spec for Scorpio. And when I think about MS' strategy, they may even make that happen sooner rather than later, since their business objectives are to migrate and sell as much software through their store, you don't want games being spec'd for XBO, when you're attempting to transition users over from Win 7 to W10. You're gonna want your exclusives to be big time sellers in the PC space to force the migration, and that will only happen if the specs move up.
That being said, Scorpio could very well be waiting on key DX12_1_2 based features that haven't been seen on AMD GPUs yet, which might be the extra year wait. I'm sure it would be a giant mis-step by MS to release Scorpio as only FL12_0.
As Per BC. As a guy coming from PC, I really do appreciate it. One thing that few people have mentioned, or I haven't seen mentioned often, is that with BC, I'm looking at a completed library. Like I already know what games I want to play, I already have all the reviews, all the expansions and DLCs to fix the game is done. The games are being presented to me in the best possible state (ignoring MP games).
That's a big selling point. Instead of buying new hardware and hoping for a game to take full advantage of it, you're actually looking backwards with that 20/20 hindsight and cherry picking all the titles that actually accomplished it.
That's something where, should Sony put PS3 BC on PS4, I think I would cave in. And If PS5 doesn't support it, there's just no way I'd buy in ever. There's just too many games on PS3, PS4 that I would have missed. I don't want to sloppy spend money everywhere hoping to justify my purchase, I'd actually much have all my games and purchases in mind and then go for the plunge (if I had to choose a secondary system).
edit: what tends to come to screen often on both Reddit and NeoGaf is: "I just got X console, what games should I get for it"
And the response is like 4-8 exclusives. Usually, maybe less.
it's not a lot when you think about it. But you alter the question to, I got X console what BC games should I get on it, and people are going to recurse this massive library of 8 years and you're going to get a ton of options.