I'm curious as to exactly what kind of content you're planning on hosting where you thing you can get 1 million unique users per day within 1 year...
In any case, you probably want to talk to Shawn Hogan @ Digital Point. Most of his traffic is NOT from his forums but recently mentioned that he deals with about 125 million page views per day and that traffic is growing about 10% each and every month.
http://www.vbulletin.com/forum/showthread.php?t=184748