Just because things are in folders doesn't mean you still couldn't have a global search feature. It already does this with voice commands on PS4, XB1.
......I can't even believe I have to justify a system having folders option.
Having a global search option--which requires people to remember every purchase they've made--doesn't fix the issue of visibility.
My Vita has a 64GB card and stuff organized into genre-related folders, and, despite the device's relatively young age, I still forget about much of the content I have on it. Same scenario with my PS3, except worse b/c it's over 7 years old--some of my genre-related folders have more than 20 entries in them, and the PS3 only creates icons for PSN content.
I'm not opposed to having a global search feature, accompanied with voice commands; but I honestly don't think that using folders for organization is the best option, especially on a device that has tons of storage and a lifespan of 5+ years. A "frequently used" content area combined with a Library area that has powerful sorting options and a stream-lined interface (aka. NOT GIANT EMPTY BOXES WITH TINY ICONS (like it is now) seems optimal for a console experience.
Oh, and I also think that the PS4 needs the ability to selectively delete content per game; for example: if I want to delete the Killzone Shadowfall install file, but leave the GB's worth of patches on the HDD so I don't have to download them all again next time I go to re-install the game.