I don't want to go to one of your parties.

To actually answer the question, the implementation of party chat, or cross game voice chat has not already been implemented because the retroactive adaptation of this chat would only work on about ~80% of old games ofter patches.

And certain developers, (EA) have said, NO.. because their games may seem inferior on some level once cross game voice chat comes out, and older EA games would not support it. These dev's were literally holding features hostage from not being released on the PSN.

The same thing happened with trophies initially.
But now since the internet has caught wind of the problem, EA has backed down and now cross game voice chat will see its release soon.

It is only a matter of time, and there is NO reason why they will not release it between this week and next week simply other than the fact that it takes time to make such additions to an online network that never intended to harbor such features from the onset.

I am absolutely confident cross game voice chat (or private chat as the 360 calls it) will see a release sometime soon.

But I am not sure of the specifics of it, or if the PSN will come out with a version where many people can exist in one private chat, (party chat) like xbl has.

Just be patient, the service will be on the PSN within ~3 months.