According to a news article:
"March 10, 2003
Celebrity's On Schedule with ReBranding
Celebrity's ship-by-ship transformation program, which is in the process of folding a host of new features into the onboard experience, is on schedule. So far, three vessels --Millennium, the "test" ship, Mercury and Constellation -- have already rolled out the new look, which aims to offer more options and flexibility -- and less regimentation. Summit's the next to get the Celebrity treatment and the company says it will be completed by April 14. Infinity's on schedule for a May 6 date and the remaining ships -- Galaxy (June 6), Century (June 28), Horizon (July 16) and Zenith (August 9)-- will be completed more or less at the rate of one-a-month."
They may have put in some enhancements already.