Early announce. The initial reveal date was pushed back from April 24 to May 21 so that Microsoft could better position the device against the PlayStation 4, which Sony announced in late February.
Full (end user) announce. Microsoft will fully reveal details about the next Xbox, including the launch lineup of games, on the eve of the E3 tradeshow in early June 2013.
Developer announce? It appears that Microsoft will discuss the next Xbox developer platform at the Build conference in San Francisco in late June, based on clues on the Build web site.
Launch. The next Xbox will launch in early November 2013.
Windows 8 Core. The next Xbox is based on the "Core" (base) version of Windows 8. This suggests a common apps platform or at least one that is similar to that used by Windows 8, and further than Microsoft could open up this platform to enthusiast developers. (That last bit is supposition on my part.)
Price. Microsoft will initially offer two pricing models for the console, offering a standalone version for $499 and then a $299 version that requires a two-year Xbox LIVE Gold commitment at an expected price of $10 per month.
No entertainment box. Microsoft originally planned to offer both a “full” version of the next Xbox (with video game playing capabilities) and a lower-end entertainment-oriented version, codenamed “Yuma,” that did not provide video gaming capabilities. But plans for Yuma are on hold and no pure entertainment version of the next Xbox will appear in 2013 (or possibly ever).
Blu-ray. The next Xbox will include a Blu-ray optical drive.
Internet-connected. The next Xbox must be internet-connected to use. This is source of the “always on”/“always online” rumors and isn’t as Draconian as many seem to believe.
Another Xbox 360. Microsoft will also deliver a third generation Xbox 360 console this year that will be significantly less expensive than the current models. The new 360 is codenamed “Stingray,” but it’s not clear if this device is required because the next Xbox isn’t backwards compatible, or because Microsoft simply wants a low-cost entertainment box alternative. (A third possibility, and to be clear these possible reasons are all speculative: The 360 simply has life left in it and with dwindling component prices in the 8 years since the original launch, the firm can still make money selling such a device.)