Right from The Windows Phone Developer Blog
The full Windows Phone 8 SDK will be made publicly available later this year when we unveil Windows Phone 8. Until then, we believe this program offers more published developers a way to explore the SDK and get started on the next wave of amazing Windows Phone apps.
So, while Windows Phone controls less than 5% of the total smartphone market you want to further delay new applications? The only reasonable argument here is that WP8 needs quality apps for the platform launch. But, is it worth it? People have paid 100$ so that they can publish WP7 apps and they will be rewarded by “please wait” tagline.
There is enough time to change the policy, but will it be enough to remedy the backlash?