If AllThingsD is correct, Tim Cook will be taking the honor of unveiling Apple iPhone 5. I guess this is something worth mentioning since the source is AllThingsD but also a note of caution from them. Apple can change their mind anytime.
I was expecting Steve Jobs to do the unveiling although he has resigned from his post. Anyway, the source also mentioned that iPhone 5 will be available for purchase a few weeks after the announcement.
AllThingsD has a lengthy report about this announcement and the choice of the presentor.