Nintendo

You can still re-download your purchases from 3DS / DSi Ware / Wii (unless it changed since the last time I checked). Same goes for Steam even for unlisted games. It’s a problem that I am still waiting to see. And even then, just copy the data in advance on extra memory (which is inexpensive when the time to make backups comes).

If your console breaks, you can buy another one, link your account, and re-download your games. You can apply the same logic on games which won’t last forever (there are notorious issues with 3DS games that are dying, and CD-based games are doomed to rot like many PS1 games at the moment). The problems you raise will potentially happen at some point, but physical games (especially those sold nowadays) have also their own problems. You can also get robbed or have a fire at your house (in which cases going full digital is an advantage).

For preservation itself, legal solutions are doing little to nothing. Even if you count physical as a way to do it (which I disagree since the games are just incomplete and in their worst state), the prices going up because of speculation makes many of them unreachable to most people at some point. Piracy / emulation remains the only way to preserve video games efficiently (but it should not be praised for consoles still in production of course, we should let them die first).