Unfortunately, "truckload" isn't an official measurement. Check out the official numbers from Nintendo!
There's going to be a ton of GameCube's ready for launch in the US as well as Japan. How many you ask?
Japan: 500,000
USA: 700,000
By the end of 2001: 1.4 million (including launch)
North America: 1.1 million (including launch)
Even though this is a huge number, I would suggest pre-ordering a GameCube the first second you get.