Ultimately, the new Taskbar is not Mac-like in any important way, and only the most facile of analyses would claim that it is. Concerns that Microsoft is making Windows too much like Mac OS X are not founded on any real evidence; the similarity is at most skin-deep.
That said, it’s not impossible to see a future where Windows also uses the same concept of the document being the window, ending the peculiar document-less windows we see today in Word and other software. It could do this by using the same approach as Messenger already uses in Windows 7; retain the Taskbar icon even when the last window is closed. In conjunction with a few extra window management operations (the ability to bring all windows of a particular application to the front, for example), Windows could offer the best of both worlds: the document-centric UI of Mac OS X, with its neatly orthogonal application and document switching, and document windows free from the constraints of their application, combined with the rapid window switching and management of the Taskbar.
