Could the Slim Launch be even higher than 550k?

[Reasonable]

Well, it kind of goes without saying that it might be higher.

This site estimates sales - there is an unavoidable margin of error, and sometimes it will be larger and other times smaller.

This is true all the time, though, so while I guess I know what you're asking, the fact is the sales for Wii, 360 and PS3 could always be higher (or lower) than shown here.

I guess what we do know is that the PS3 saw one heck of a boost for HW on the back of the Slim, and now all eyes are on how the sales settle.