I doubt that they will have 1 million by the one year mark (April 28th).
The last numbers we were told was by Steve, and then in January they only had 500,000. I'm guessing that at the one year mark they will have more like 750,000 at the most.
April 28th, 2003 - 200,000 song debut
January 21st, 2004 - 500,000 songs (9 months in)
April 28th, 2004 - 500,000 songs + 3 months of additions
I think that even 750,000 would be rather amazing and 600,000 more reasonable. I'm sure Apple will have a press release on it. (Hopefully to include songs sold in year one and the outcome of the Pepsi giveaway).