Speculation as to why WP8 will be a success.
Let me preface by saying that this is just a wild guess, but this is my response to all the posts I have seen saying that Microsoft will have a difficult time in the smartphone space since it currently has such a small market share:
Microsoft may be behind in the smartphone race now, and may not catch up overnight, however, they will most likely become very competitive in the tablet space. Windows 8 tablets will jump to the number 2 space quickly (I think most people agree on this) behind the iPad. And I think it will start to match iPad sales when the general public start seeing more and more people using the surface RT/pro and OEM products.
Where does WP8 fit into this? Well from my anecdotal experience, a large portion of iPad buyers were people who had the iPhone and really enjoyed it. For Windows, I think this will happen in reverse. People will use Windows tablets, whether at work or school, enjoy the product, and this will lead them to purchase a windows phone in the future.