I don't think this is bad: it's exactly the model being used for Windows 8(.1) at present.
We've got Nokia (now to be absorbed by Microsoft), who will likely continue to press forward with the luxurious design and great mobile imaging technology we've come to expect. For people concerned about Windows Phone losing what makes it unique: just stick with "Microkia." Just like Microsoft's Surface line: it's unlikely to change.
However, whilst you can stay under Microkia's umbrella, you can also branch out to potentially new and innovative ideas from other OEMs.
This is beautiful, actually. It's just like Windows 8: we've got the perfect harmony of a combo between Apple's model and Google's model. If you want streamlined hardware and software, stick with Microkia. However, you also are respected to make your own choices about the devices you use, and can easily switch OEMs if they have something that better catches your eye.
All this: without having to relearn the UI every upgrade, you get to keep your data and let all of it migrate, while you also aren't being forced to only have the option of one new device per year.
This is just awesome, I'm very excited. Microsoft is absorbing the strength's of its competitors, and very few of their weaknesses. Be not sad, my friends, rejoice! A new era of Windows Phone and Microsoft is dawning upon us: and it is glorious!