Out of curiosity, out of all the apps I'm assuming games are the main culprits of being storage hogs, is that right? Looking at my current phone I don't use a lot of games, and am only using around 600MB in space. Chrome is my biggest app at roughly 66MB, where my biggest game is Super Stickman Golf at 33MB.
I'm figuring I'll likely be plenty fine with the 16GB S4, knowing I only have 1GB of space on my Evo 3D and I'm not close to filling that up yet, and the fact I'm not a big mobile gamer. I'd have to use up more then 8x more space then I am right now, and I don't see that likely happening over the course of the next 2 years.
I'm assuming the majority of people with similar usage habits to mine would likely never run into a storage space issue with the 16GB S4, and if space was getting tight, you can get a 64GB SD card for documents and media. Does that sound logical?