Apparently the pre-order CEs will be shipped the day before release date (ie tomorrow), so they will "start arriving" on release day. But indeed, there's no guarantee that they will actually arrive on release day... it may be a few days later.
Those who ordered a Kickstarter CE already have the game code on their account, so for them this isn't relevant... they already have access to the game and the digital goods on release day. This only applies to the 1000 people who were fast enough to get one of the left-over CEs.
[edit] on a positive note, though... this means that by the time you start playing, other people will already have run into the most game-breaking bugs and there may already be some workarounds or high priority fixes... so you should have a more stable playthrough
