Here is what Chris Sawyer said about it back in July 2000.
"Q. Have you any plans to create an RCT 2?
A. I'm sure it's something I'll think about doing sometime. Roller coasters still fascinate me, and there are many areas where RollerCoaster Tycoon can be improved. However, I'm waiting for technology to catch up enough to enable me to do what I really want to with the game. I also don't want to 'burn out' my interest in the game, something which might happen if I started work on a sequel this soon."
Source:
http://www.strategyplanet.com/rctuk/chrissawyerinterview.html -------------
Cyclops. 1900 feet of CCI goodness.