Good question. I would hope the updates are already ready and that those who preordered (read: just about everyone at this point) will have access to the updates upon installation and boot up of the game.
If they wait till the 29th to roll it out, I'll be mildly disappointed; fact is, I don't plan on starting a long term MyLeague until I run a few tests with it to determine what the AI logic/sim injury rate/progression rate is like on various different settings. But I'd hope they don't make us wait for updates until the 29th if we preordered ... otherwise the early release doesn't really matter, right?