I'll just parrot a bit what some others have said, also have some partial solutions and references to groups working on the issue below.
While digital copies are far more convenient for the most part, there will always be demand for the physical. We see this trend shadowed in nearly every media market(except pc for whatever reason), though I think the Bluray/DVD guys have got it right. Most of these include all modern versions of the content, both physical and digital. It was actually surprising to see the film industry do this instead of attempting to make people buy multiple formats separately.
I haven't bought many modern CD's/Vinyl - do any of these do the same sort of thing as films? Including digital download and whatnot. (though you can always rip after purchase...)
I'm going to mimic the fears of a few people in here; digital copies run the risk of a failure in long-term support. You don't ever actually own the thing, you're basically renting it indefinitely. DRM-free or soft DRM digital copies alleviate this somewhat, because you can store backup copies in most cases. Hell even with steam, you can make backup copies and login offline *(see below) - so I figure at least steam copies you can pretty much keep forever unless they have always online DRM/authentication. That stuff is the worst offender, and though I enjoy plenty of those types of games you never know how long they will be supported.
Solutions and Silver Lining:
You can also port/copy your steam library to any other computer and login offline. As long as you don't connect to steam, associated accounts won't get flagged as far as I know. You have to remove the stuff afterwords though if you have a legitimate steam account. Did this a few times to try out a game in my brother's collection before they had the family share stuff. It's legal grey area of course, but when the subject is backing up your own games, I feel like using a work-around like this is completely acceptable and even essential. Especially in cases involving thousands of dollars in games.*
There are some groups (Library of Congress and History of Science and Tech at Stanford come to mind) that are working to preserve digital media, so if we are truly concerned about having access to our digital media into the future, we should do what we can to support these groups and types of actions. As for myself, I've got my favorite digital copies of steam games on external hard drives (need to start doing this for console stuff as well), and as long as they are well kept/updated they should last quite a while.
*Disclaimer: I do not condone, nor am I trying to teach theft. Do not use/look into this method unless your goal is to protect your own existing investment in your library.
