This may not exactly be the news that current Windows Phone 7.5 device owners are looking for but it does answer a related question: Will current Windows Phone 7.x applications run on Windows Phone 8? In a recent blog entry, Microsoft confirmed that they would (their emphasis):
With regard to existing applications: today’s Windows Phone applications and games will run on the next major version of Windows Phone. Driving application compatibility is a function of Microsoft’s commitment to its developers. Regardless of what we release in terms of new developer features and functionality, we have made a large investment in protecting your existing investments.
Right out of the gate, Windows Phone 8 devices will have access to some 80,000 apps (and likely more by then).
As for whether existing Windows Phone devices will be upgradeable to Windows Phone 8, hopefully past rumours are untrue.
Read more: Windows Phone Developer Blog