A few things of note:
1) Murtazin is no MS employee, this is entirely based on conjecture, and it does not jive well with the direction that MS has been pushing for these last 2 years. My bet is that this is mostly for publicity. I mean, the only person consistantly right on rumors are Mary Jo over at zdnet, and the folks over at WP Central, and even they get hoodwinked from time to time.
2) Windows 9 is not expected until Q4 of 2015, and WP9 is expected to be released after that (because MS is not so coordinated as to launch multiple platforms at the same time). So we are talking about very late 2015, and more likely early 2016 for the next WP release. Any phone you buy within the next year or so will be out of date by the time the new OS is released. Even if you pick up a phone towards the end of life I bet you will still get decent support on WP8. WP7 was the red headed step child that MS did not know what to do with. It was a dead kernel with a immature UI... kinda hard to support that when you are trying to unify platforms. WP8 is similar to win8, and will still get at least some attention after the release of win9.
3) Win9 and WP9 will have a new interface... the same way that Win8.1 is a 'new interface' from Win8. Still tiles, still a flat UI, but hopefully matured, more feature-full, and intuitive. There is a possibility that they could move to something else, but it must pass the test:
-It must work well across a varieity of input methods
-It must work across a variety of form factors
-It must be the same (or at least very similar) across WP, Win, and xbox
Tiles seem to be a great compromise here, and I would be highly surprised if they moved to something else so quickly.
4) It is sounding more and more like WinRT is getting the axe and the planned features will get rolled into WP at some point. The idea (at least in my mind) is that by the time WP9 rolls around then you will have the option to have dockable phones. It would be a phone while on the road, and then moves into a tablet mode with a limited desktop for use at home or in the office. I could be wrong on this, but that is where I see things headed.
5) Windows, Windows Phone, xBox, Windows Server, and MS services (skydrive, outlook, office365, etc.) all need tighter integration, and we have seen nothing short of a revolution on unifying these product lines over the last 2 years. A few years ago you would not think that the same company made all of those products, and now they all share a common visual branding. Today they work together on at least a surface level, but by the time win9 rolls around they will all be part of a value building ecosystem. Somebody joked about paying a yearly subscription for Windows, and while unpalatable to some, this may not be an all together terrible idea so long as they do not offer the same scam of a deal we have seen with the $100 Office365. Actually, that is really not such a bad deal if you really have 5 machines. But if you are like me and only have 2 machines... not such a deal.
But the point is that if they really are pushing unification of software and services then I could see some sort of $1-200 per person subscription plan which gives you all current software, unlimited xbox music, discounts for 3rd party apps in the app store, discounts on windows hardware (WP, tablets, laptops, xbox, etc.), xbox gold subscription, and other such perks. Trick is that they need to price it more appropriately than they did with office365 because there is not a 'one size fits all' in this market.
6) Windows 8 is the coreOS for xbox, windows, and windows phone. It is based off of the good old NT kernel, and is finally to a point where it can run on just about anything you throw at it. But while the NT kernel is shared, all of rest of the OS is fragmented out so that they can have different UIs, drivers, networking, security, and other features on different devices. I think that win8 was the 'great experiment' to see if they got things right on modularizing the OS. Windows 9 (and the updates leading to it) will be all about unifying these modules so that you can get as close to the same experience across devices within the limits that form factors and input methods allow.
7) I think that the start screen changes to be found in WP8.1 will be very telling for the direction that MS wants to go with the design language. WP seems to get the newest direciton on the Metro UI, while xbox and windows follow with an update. Windows 8.1 brought a lot of WP8 features to the desktop, and I feel that WP8.1 will lead the way on the next generation of the start screen, and where it is headed.
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