Stephen Chapman over at ZDnet did some investigating into some Microsoft job postings and employee résumés. What he found was evidence pointing to the possibility of both Windows 8 and Windows Phone 8 being built on the same kernal.
Résumé of a former Program Manager:
The responsibilities included program managing software update features to provide device update technology that enables end-users to update Windows Phone OS with a new set of phone features including bug fixes. In this role, I delivered a set of functional requirements specifications for the major update components to enable image updates for the next generation Windows Phone OS (aka Apollo). They are Packaging System, Imaging System, Flashing System, Update OS, Update Validator and Update Application. Also drove and tracked early investigations for the Windows 8 and Windows Phone 8 OS convergence to create Mobile SKUs.
Résumé from a HTC Senior Product Planner:
Owned the advanced planning relationship with Microsoft; drove Microsoft “Apollo” product planning discussion and led HTC cross-division feedback. Identified high potential partners and technologies; initiated/participated in new partnership discussions; ensured the relevant technology integrations and strategic alignment.Restructured communication channel between the planning and field communication team; greatly increased the sell-in material accuracy and increased the overall update rate by 50+% Spearheaded the 2012 Windows mobile phone product roadmap.
Chapman doesn't stop with the above, here's another résumé quote that will be of interest to many users:
Design and development of new features for Windows Phone-8. Implemented the ‘Voice-Compose’ (STT) and the ‘Read-Aloud’ (TTS) features for native email-clients.
Finally, we have a quote from a résumé that lists Windows Phone updates:
Launch readiness for account within region of responsibility (e.g. Mango, Tango1, Tango2, Apollo, etc.)
While the above quotes aren't concrete proof that any of it is true, we can at least speculate that Microsoft are pushing for a unified ecosystem where PCs, tablets and phones all run the same kernal and UI, that they intend to bring voice control to emails and we're already aware of the Tango update being minor so two minor updates seems a possibility.