Just my $0.02, but I wouldn't count on a 32GB or 64GB version of the GS4. Reason: The Note 2 only came with 16GB option and they even discontinued the 32GB model GS3's. The 16GB models of EVERYTHING are always the best selling (just go ask how many 32GB or 64GB iPhone's they sell and you will see it's no different) because to the average person it's just cheaper. The only reason they even carry the larger iPhone's is because Apple makes them (something Samsung needs to start doing). Otherwise, if it were up to Verizon they wouldn't.
If a larger capacity GS4 ever came, it'd be late this year, long enough to where early adopters cannot return/exchange their 16GB models. Verizon is a very 'corporate' company and they will not do anything that hurts their own sales or results in high returns/exchanges. So, for those waiting you're really playing a dangerous game because likely it'll never come and IF it does, it'll be fall in the fall at earliest. Even the Developer Edition is only 16GB.
I agree that coming from a 32GB S3 to now a 16GB S4 is a bit of a slap in the face, but for now I manage mainly because I don't game too much on my phone so I can for the most part deal. Still, if I had the choice I'd get 32gb or 64gb just for the sake of longevity. I'm crossing my fingers that we'll see a fall release of a 'limited edition color' GS4 with 32GB or 64GB of storage. I could possibly see Big Red do that, but even then that's depending on how their line up for the fall is.
Verizon is also staying away / being excluded from the Google Edition of devices, probably because they were kicked out of the Nexus program for not allowing Google updates. No OEM probably trusts them with a 'nexus-like' device because Verizon will still want to control updates. It sometimes sucks to be on Verizon, especially when it comes to devices, as they are now officially dead last when it comes to options.
If it wasn't for the fact that I'm grandfathered in to an unlimited everything plan and the recently announced AWS support for the GS4 I'd likely leave altogether. Verizon, hear me now: if you ever force me to get rid of my unlimited, I don't really have much of a reason to stay and will just go to AT&T for better phone choices.