The idea (as far as I understand it) is that from an end user perspective they won't need to get confused by the 'Mobile' name or any numbers. They can just look for a 'Windows Phone' to go with their 'Windows PC'.
Why this may be good:
- A unified marketing message may drive adoption leading to more people with Windows Mobile based phones.
Why this may be bad:
- In that the operating system will still be called 'Windows Mobile' this may lead to some confusion.
- As soon as there are multiple versions of Windows Mobile being advertised as being "Windows Phones" there are likely to be software compatibility issues. This will require knowledge of the underlying operating system, so the user will have to know which version of Windows Mobile is being used.
- Users may expect software that works on a Windows PC to work on a Windows Phone. - It' wont. (This has been an issue in the past, when users first saw 'Windows' on a phone.)
What the outcome of this change in marketing message turns out to be will be seen in time.