According to Bloomberg, Apple will be unveiling its new lineup of thinner MacBook Pros at WWDC, the company's annual developer conference, which will be kicking off on June 11. Apple is also expected to announce the release date for Mac OS X Mountain Lion as well as preview some new iOS features.
The new MacBook Pros are expected to feature Intel's latest 22nm Ivy Bridge processors and possibly a high-resolution Retina display. Bloomberg's sources have confirmed that the new MacBook Pros will have a slimmer design, similar to that of the MacBook Air. They also confirmed that Apple will be using flash memory to help speed up boot times and to extend battery life, although it's not clear whether it would be used in conjunction with a conventional hard drive or used exclusively as is done on MacBook Airs.
The sources did not confirm whether or not the new MacBook Pros would feature the much rumored Retina displays, but Intel's latest processors can handle the resolution and evidence in the code of the latest OS X Lion update suggest that Retina displays could indeed be shipping on the refreshed MacBook Pros.
The Mac-centric event is expected to also bring us more details on OS X Mountain Lion, which was first previewed back in February. It will likely get a more detailed rundown along with release date announcements. Additionally, Apple may preview some new iOS features, but the bulk of the event is expected to be on Mac developments.