Answer found from Superuser: http://superuser.com/questions/571003/how-to-convert-gif-files-to-png-or-jpeg-in-os-x-with-command-line

Using the sips command, almost any image format can be converted into another, like so:

cd /directory/with/gif/images/
mkdir pngs
sips -s format png ./*.gif --out pngs

This will create new images with a png extension in the pngs subfolder to match the gif version.