I'm ready a little more... seems like a limited to Window RT App Program... the App OS.
+ You can use only the Windows APP OS and its 3GB reversed memory.
Edit - More... that's official.
UPDATE: But not at launch. Microsoft's Marc Whitten just told us that devkit functionality will be added at a later date.
Seems like MS is revising all the Xbone plans from zero... so the new plans needs do be developed.