Here is a response I got from Toyota Motor Sales, USA back in early May 2007. From what it says, I don't expect it to hit the floors until September(IMO):
Thank you for contacting Toyota Motor Sales, U.S.A., Inc.
We appreciate your interest in the 4Runner.
Information on the 2008 4Runner will be available closer to the tentative launch date in August. To receive information as it becomes available, please subscribe to our Current and Future Models FAQ (Frequently Asked Questions).
We are committed to manufacturing high quality vehicles that exemplify innovative design, styling, dependability and durability. In an effort to maintain the quality that is evident in our previous vehicle models, we continue to pay close attention to the detail in our future models.
Again, thank you for your interest!
Your email has been documented at our National Headquarters under file #------------. If we can be of further assistance, please feel free to contact us.
Toyota Customer Experience