That theory is flawed cause that hasn't stopped the iphone from doing well
Theory makes since unless you seriously think market conditions in mid 2007 are equivalent to those in mid-2012.
And I hope you don't.
WP7 isn't competing against Palm, Symbian, WinMo, and BB OS4 or whatever. Pretty much all of those are dead or on the way out.
WP7 is competing against iOS 5.1.x, Android 4.0.x, and BB7 with BB10 on the horizon.
Smartphones are no longer "business devices" but also mainstream consumer devices. Device consolidation is at an all-time high, and with the way the ecosystems are setup users are less fickle with platforms than they used to be. They will stay where they have made decent investments on apps/media/games/etc.
Microsoft could have been a major player today, if they weren't slow as molasses and sat on their thumbs to give us the venerable (lol) Windows Mobile 6.5. Google was creating a OS that looked much like BB/WinMo and after iOS was unveiled they changed very quickly and delivered something radically different. That bode well for them. Palm, Microsoft, and RIM were not so quick to change, and they're all paying (or paid) for it.
Agility to respond to market disruptions and changes is necessary. Google had it, Microsoft and RIM still don't have it. That will continue to hurt both of them, although BB10 is looking to be a more completely product than Mango is right now so they may be able to save face given their marketshare world-wide is still respectable.