Shuhei Yoshida, the President of Sony Worldwide Studios has crushed the hopes of the PS3 ever getting cross-game voice chat. Stating that it will never happen due to the console's RAM being almost entirely consumed by the System's software.
"Once a game gets RAM we never give it back, it’s not possible to retrofit something like that after the fact… The game has to use its own memory to do [in-game voice chat]. There’s always voice chat in the game. But it’s a part of a game feature. It’s not a part of an OS feature. That’s the reason in terms of the ability to have voice chat across different games.”
Whilst the PS3 may not be getting cross-game voice chat. The PlayStation Vita on the other hand will feature it as it carries 512MB of RAM, double of what the PlayStation 3 has.