The biggest problems a puppy will have being separated that early is that they lose out on essential social skills that only their mom and littermates can teach. The younger a dog is removed, the more likely it is to have problems with mouthing/biting.
I think we have something like this on this site, but I can't find it right now. It gives an overview of what puppies learn at different stages.
http://www.ddfl.org/behavior/pup-dev.pdf