There was no event for the original plastic macbook, if i recall.
My guess is quiet update to mini and macbook next week and imac event later in two weeks or so.
True.
The thing is, there is no way to tell. Sometimes big things have no event and small things have one. For example, the change from PowerBook to MacBook Pro wasn't that much of a change (only the internals were changed, and the addition of an iSight), and it had it's spot at Macworld 2006. The iBook to MacBook was a drastic change, completely overhauled, yet it was just an update on the website, without any event.