Imagine the next GTA game, fully developed for the next gen platforms, blowing the 200GB barrier easily.

Always remember. Games aren't priced higher because they need to be, just because they can be.

Most games aren't massive open world playgrounds, with a constantly updated multiplayer mode, and MTS to boot. So it's only natural that this game's file size will be 120 GB or more by the time all the updates, and DLC are out.

I'm not sure how much extra space it takes to go from current gen graphics to whatever next gen is, but that will be how much bigger games are.

Edit: I feel like next gen there will be two types of games. Those that still get a decent physical version, and those that don't. The ones that don't will be the same kind of games that currently come with MTS, content carving, etc. I avoid those types of games at all costs, because they usually aren't very good. 

Quad layer 128GB Blu Ray discs for PS5?

I don't think the PS5 will have an optical drive at all. The problem isn't so much capacity, but more the slow ass speeds of those drives. Copying 200 GB would take ages! Ain't nobody got time for that! Internet speeds will only increase until then, so digital is the way to go. Of course you can't ignore sales at local stores, so I think we will be buying codes in nice packages next gen, just like we already do on PC. You punch that code from the store into the PS Store and download your game and that's that. That people won't be able to sell used games is just a nice little bonus for Sony. They want things to be that way. They want it so bad, you wouldn't believe it, but the time wasn't ready back when the PS4 launched. But I think we will be there soon. People also used to refuse steam and now they all love it and don't buy games if they aren't on Steam and shit. It will come to our beloved consoles, just wait.

I know people don't want to hear it, but the days of physical media for games are numbered. Oh, and let's also hope that the PS5 comes with an SSD right out of the box. HDDs don't have a place for games in 2020. They're just too friggin' slow.

Ok, you can hate me now. =P

Rather the opposite, downloading 100GB is out of my reach with a monthly data cap.

I wish we could back to playing from disk. I can have less and less games going without the hdd getting full. Read and seek speeds are the problem though with physical and there doesn't seem to be any faster affordable alternative on the horizon. 100GB cartridges will not be cheap either.

If Sony went digital-only I would switch to PC in a heartbeat. 

You are aware that PC is digital only as well, aren't you?

Yep, but the main reason PS4 is my main system is the ability to own my own games. Without that, I'd regulate it to a secondary system for exclusives. 

Since the last gen PC has been my main platform for games, I own 1 or 2 consoles just to play exclusive titles only.