Should I buy the MBP retina now or wait for the new one?

I wanna buy a new MBP retina 15" before my uni starts in fall so after like a month and a half. I already have a 2011 MBP but wanna get a new and better one so I'm just wondering what is the latest 15" retina by Apple? And when is the approximate date for the release of new retinas? Like I mean if Apple has a date for new releases like it has for iPhone and iPad usually like to know if it worth waiting or not

They may quietly release newer ones in October.