For reasons that don't seem to make much sense, the Windows Phone 8 SDK will be made available to everyone, but not until a day after the launch of the phone.
update: The SDK is now available for download to MSDN subscribers and to the public from: http://www.microsoft.com/en-us/download/details.aspx?id=35471
More information will be announced at BUILD which starts tomorrow, which might provide some rationale for the delay. No exciting new features that could possibly have made it necessary to keep the SDK secret have been announced at the WP8 launch.
We have some new apps for Twitter, Facebook and Skype. The phone will support multiple users via the Window Account - i.e. just like Android and your Google account. You will also get access to Pandora the radio streaming service free for a year and your photos will upload to SkyDrive automatically.
As at previous presentations ,the emphasis seems to be mostly on the hardware, the services and a vague promise of integration and unity across the entire Window 8 line - which we know not to be quite as convincing as Microsoft would like us to believe. Delivering the presentation, Steve Ballmer promised wall to wall advertising coverage for the new phone.
There was nothing announced at the launch that that could possibly have required that the SDK be kept secret.
In fact it is arguable that so little that was new was announced at the launch that even the excitement that holding back the SDK was supposed to achieve didn't really materialize. In other words there was no - "one last thing" moment.
So after months of waiting for the SDK we still have another day to wait. Tomorrow developers will discover what they should have been told with some rapidity if Microsoft really wants to keep everyone on board. It is amazing to discover that as Steve Ballmer introduces the new software to the world most developers still don't know what is necessary to create apps for the device and still don't know the details of how their existing WP7 apps will run on WP8.
More information some time tomorrow.