It was just last week that Nintendo of America's Perrin Kaplan confirmed that Wii component cables will be available on launch day at retail chains, specifically citing Best Buy and GameStop as examples. Ironically, this confirmation came after she remarked that she had misspoke when announcing Wii would be region-free (turns out, that's about as far from the truth as possible).
If you absolutely need Wii in 480p from day one, order now. Otherwise, wait it out or select the cheapest shipping option.
[Via Skeptical Gaming]
[Update 1: clarified how we got the December 5 retail date.]
[Update 2: Just a heads up, many people are reporting the cables are now back ordered, rendering it not likely to arrive on launch day. Be careful when ordering.]