I was told at GenCon that it would require a live connection, which makes sense if you think about it. It is a web browser app after all as I understand it.
My deciding factor will be, if the current product is the "offline" mode and the migration is NOT one way so i can use either product, then I'm a happy camper!
Its how they handled the iPad (as a license and not its own product) so I have confidence that Rob is going to make us happy and not sad