No, the goal is for the current user experience to remain the same. By default docker will create a sparse file, loop-mount it, and use that for all containers. There is some magic in thin provisioning which allows for dynamically resizing when needed. We will add more details in the docs and mailing list in the coming weeks.

The best place to follow progress on this is to track docker-dev (https://groups.google.com/forum/#!forum/docker-dev) and the #docker-dev irc channel.