He'll definitely have a speech at the '04 convention, but not the keystone speech. It'll probably be one of those early afternoon ones that is overlooked.
2004 was a Democratic year in Illinois, so Obama still wins, but it'll be a closer election in TTL (of course). Remember, he's still the only African-American Senator at this time, and unlike his predecessor Moseley-Braun, will be treated quite well on every talk show and have a natural cult of personality formed anyway.
By 2008, he'll have *some* pressure to run for the Presidency, and may even give it a small try. But he'll at best get the running mate position and more likely a cabinet post (if he accepts it) in the almost certain Democratic presidency to follow.
If he stays in the Senate, he'll be running come 2016 (or 2012 if the President is Hillary Clinton/Chris Dodd/John Edwards/maybe Joe Biden).