As a sign that Microsoft's next-gen mobile OS is almost ready, the company says developers can apply to be part of its Windows Phone 8 SDK Preview from next week. Any developer that has already published apps will be able to apply, but Microsoft's Todd Brix notes that "program access will be limited." The final SDK will be released to coincide with the unveiling of Windows Phone 8, which we expect to drop on October 29th, but Microsoft wants to make sure developers get their apps get ready in time for the impending launch.