Question: What do I have to do if I realize my current hdd is too small? Somehow I have to get my old data on the new one. How?

Ouch.... How much well it cost? 

I know 500gb won't be enough but I won't upgrade until I run out of space.

I've looked this all up for my PC, the loading time differenecs aren't that much since the games aren't really designed to take advantage of the quicker load times. My SSD in my desktop doesn't have any games on it, because the 128GB one I got cost as much as a 1TB HDD. If you want an SSD of any useful size, then you are basically going to have to pay the price of the console again and that just doesn't seem worth it.

A hybrid drive would be an alright answer, since in theory it would put the game you are playing on the SSD part and keep your legacy stuff on the HDD, but I doubt that the PS4 will actually be designed to enable that feature

I don't know about the other consoles but on PS3 I made a backup on an external HD, then plugged in the new HDD onto the console and transferred the back up to the new HDD. After that everything was how I left it before changing the HDD.

I only know PS3 method... not sure if its changing on PS4 :)

At the moment, you would have to back up your data - save/profile stuff (its worth removing the games in advance)... probably can do that on cloud saves. Then there is an option to deauthorise the disk (cannot remember precisely).. you then put in the new disk... create your profile again, maybe patch.... install the games and bring back your saves/profiles.

Some info here.

http://uk.playstation.com/ps3/support/general/detail/linked347570/item347531/Replacing-the-hard-disk-(other-models)/

Additional links on the right hand side.

Issues I had when i did it was with patched games not working with my saves etc.

I hope the PS4 is more straight forward with its automated system, but we'll see, I would rather upgrade day 1 to prevent hassle in the future. :)

That's a good question, and I'm on the fence regarding this.

I'm aware that 500GBs probably won't be enough, definitely not if I would want to have a lot of PS+ games on my HDD. My stock 120GB PS3 HDD wasn't enough even without PS+ games. So I could replace the 500GB stock out of the gate, I would probably go for a 1TB hybrid drive, or 7200RPM HDD 1 - 1,5 TB. SSD is out of question right now, because of the price.
On the other hand, SSD's prices are going down on a fairly steady rate, so maybe if I would wait until the 500GBs stock HDD would fill up, I would be able to afford a 1TB SSD, which I would easily want the most out of my options.
I'm leaning towards the second way right now, but we'll see what happens.

500gb will be enough, for a while. I prefer almost all digital (less I have to get off my ass the better) so with these 50gb game downloads apparently, I'll need to upgrade.

I already have a 1tb in my Ps3. Still haven't decided weather to keep or sell it.

Thanks for the answers, guys!

i will buy a 1.5 or 2 TB hdd for my ps4, moving the 500 GB from the ps4 into the ps3, because ps+ will continue flooding my hdd.