That's just it, there wouldn't be that much of a difference with the upgrade. We'd see slight FPS and/or res bumps which would likely not be enough to make the majority of the previous version's adopters upgrade. Console players upgrade when the next gen hits because it comes with an obvious bump in power. Say what you will about gen 8 not having as much of a bump from 7 as 6 did going to 7, which is true, but there is a clear gap regardless between PS3 to 4 and the 360 to the Xbone. That's what I mean by "special attention", the difference in performance wouldn't be enough.
For enthusiasts like a lot of us here, maybe, but average joe console gamer that makes up the majority of the console consumer base, no. I haven't thought of getting the N3DS because I know it's only a minor boost to the hardware, I knew that when it was coming out. I would wager the majority who upgraded were coming from an OG3DS, really wanted Xenoblade as it was excluvise, or were tired of the bolt on second stick on previous models and wanted to use the nub.
To the final point, I understand the OP is coming from a hypothetical future where devs shouldn't have a problem supporting multiple versions, but in reality my previous two extremes are the way I see it happening if we got minor upgrades to the specs every two years until a major upgrade hits. Hell even iPhone models eventually just don't get certain apps or updates any more as they're abondoned for the sake of more current hardware. That's honestly not the future I want, to have my base PS4 become less desirable over time as the PS4.5 etc. is getting the best versions of games to the point where having the original is a detriment (ofcourse granting this extreme is what happens over my alternative). I have a PC I just upgraded from a 7970ghz to a 980ti after using the 7970 for almost 3 years. I did so to get the best expereince at the settings I want at the res I play at. I don't want to have to worry about the same on home consoles, that's not where their strength lies.