There probably won't be a pre-load. They will probably be working on the game right up until it's released.
I don't think that 99% of the files will be known. Last (big) beta patch was over 1GB so I will go with wazups2x on this one.
Who cares ?!
Maybe people with worse connection who wants to be on battlfield by day one ?
We already have the biggest files - maps etc....