Google has confirmed the recent rumors, and those in the US will be able to purchase Glass without an invitation on April 15th. This purchase will fall under the current Explorer program, which is to say you'll be paying $1,500 plus any required tax. But while the invitation requirement will drop for the day, it seems there are still some limitations in terms of available spots.
Google mentioned they will be opening up "some" spots, further clarifying how "the number of spots available is limited." Basically it seems those ready to make a purchase should be prepared to do so right at 6AM PST, or shortly after.
Purchases will be available on the "How To Get One" website and Google is even including a freebie. Those making a purchase on April 15th will have the option to choose a free shade or pair of frames.
Bottom line here, this is the latest method Google is using to expand the Explorer program. In the past we have seen them offer some spots at Google I/O and through #ifIhadglass. There had also been times when Explorers were given invites to pass out to friends.
The timeframe for a regular consumer launch remains a mystery, but for now that is expected sometime in late-2014. There has also been plenty of speculation in terms of a consumer price, but again, nothing has been officially announced by Google just yet.