In the US, the 1998-2009 Toyota Corolla has a timing chain. There is no prescribed replacement interval for a timing chain.
http://www.toyota.com/help/faqs/serv...ing_chain.html
Your dealer is just sending out a generic mailer to get you into the service department - it is not specific to your vehicle. Besides, maybe you have another car, or know someone who does, that could use a timing belt replacement.