It isn't as trivial to revisit and change older games as you might think. The reason more older games have not received 60fps bumps on the new consoles is because to republish updates you need to rebuild games using the latest console APIs and they often require the latest middleware, and that sometimes brings incompatibilities with older games which is more work.
It's less challenging on games already still in support and new games to come.
Not that I think any developer would do this, but here's a scenario where it wouldn't be so arduous.
On PC, games are scalable via user configuration of options available for the game. You could do something similar on console while still keeping the simplicity of console gaming.
First, you'd have to have a console maker that commits to support for whatever APIs and environments are used across a range of consoles.
Then, ensure that your game is scalable as is usually the case on PC. Then, instead of having numerous gamer accessible configuration options (to preserve the "console" experience), have those options available to the console maker.
Console maker could then scale settings up (or down) whenever they release a new console. They can go so far as to enable extra features that couldn't make it into a console release (but exist, for example, in a PC release) due to console performance profile when a new more powerful console is released. They could also then reduce or even disable rendering features if they were to release a less capable console in the future. A practical downward reduction limit would be the PC versions lowest configuration settings.
For any developer that is going to release a PC version most of that work is already going to be done due to the existence of a PC version. Granted some extra work may need to be done on console to expose scalability settings and allow the game to scale on console. But once a game is release, if the developer will not or cannot update the game for new hardware for whatever reason, the console maker could then opt to do that if they wanted at minimal time and cost investment.
Obviously, this would be more difficult for console developers who currently do not do the PC version of a game in house and instead rely on 3rd party developers to port their game. IE - game developers who don't know how to scale their engine and rely on a 3rd party to do it for them.
Regards,
SB