I heard that it will be available for download from Microsoft, but at over 200MB that will not be an option for people on dial up connections. The only other way to get it will be on a CD direct from Microsoft because they will not be releasing it to magazines like PCA so that they can put it on their cover discs. You may have to pay the shipping costs though.
If you want SP2 now, you can download it from click here
But be warned, these are the estimated download times for the 270mb programme: 56k 11hours- 128k 4hours 48minutes- 768k 48minutes. Not allowing for resumes or broken links. Best to wait for the official cd, I would think.