The Ultra 64 became the Nintendo 64. Its codename was Project Reality.
Yup. And the Gamecube (codenamed: Dolphin) was almost named "Star Cube" at first, which was strongly supported by Hiroshi Yamauchi himself. Glad that didn't happen.
OT: I really hope the name does change. I vote for Wii 2, or even better, Wii HD (confused people be damned!).