Rockstar has released a special Q&A about GTA V
Here is some of the more important details
“Hi R*, as you said GTAV will be the biggest game that Rockstar ever created, normally it should be the biggest in size too. So how you are going to solve Xbox 360 disc limit issues? I mean will GTAV have many discs (on Xbox 360 platform)…?”
Grand Theft Auto V is the largest and most ambitious game we have yet created, and takes full advantage of every ounce of processing power available in the current generation of consoles. In order to provide the best possible experience for such a massive and detailed world, the game will have installation requirements on both Xbox 360 and PlayStation®3 systems. For Xbox 360, Grand Theft Auto V will ship on two discs; Disc 1 will be used for a one-time mandatory install and Disc 2 will be used to play the game. After the install, players will be able to enjoy both Grand Theft Auto V and Grand Theft Auto Online without any need to switch discs.This initial install will require an Xbox 360 Hard Drive or an external 16GB USB flash drive with at least 8 GB of free space. If using a USB flash drive it must be at least USB 2.0 with a minimum 15mb/s read speed and formatted for Xbox 360 use. A new USB flash drive is recommended to ensure optimum performance. For PlayStation®3, the game ships on one disc and will install content as soon as you insert the game. The install is roughly 8GB, and players will be able to play as soon as the install is complete.
“Will we ever see some GTA V gameplay?”
Yes. Soon (or in September if you don’t want to see it before you play it… it’s up to you) – the first Official Gameplay Video is on its way...
More info about character switching is detailed in the link above.