A post by MG Siegler on TechCrunch has made speculation that that the next update for the OS X Lion for developers is going to be a "GM1" update which means it is a Golden Master (in other words the OS is completed) But this is only the Golden Master candidate which means that it could happen to be uncompleted with further testing.
This is now a month after developers received the preview or beta version of OS X Lion. With further testing from developers Apple was able to fix any minor bugs or issues that's why the Golden Master update is in the loom.
When Snow Leopard's official release to the public, it was just a few weeks before the GM for Snow Leopard was released. So if everything goes well with the GM for OS X Lion, it could very well be the same. Or it could land up being released at Apple's WWDC (World Wide Developers Conference)
The WWDC will be held on the 6th June this year. Can't wait to hear the news on the GM, will try make an update for any news in further posts.