Today Microsoft announced that they are near to the final release of WP8 SDK tools for developers after doing several testing by selected partners and developers. Though the final WP8 SDK will be available publicly later this year but they are going to open applications for limited developers.
If you are interested to getting your hands dirty with the new bits, read out the complete post for details.
After installing Windows 8 RTM, I was facing an issue that says "Windows can't activate right now. Try activating Windows later". I tried it multiple times but couldn't figure out what was the actual issue here.