I have just created a Node module that deals with PSD files from the CLI. You may use it with as many files as you want with just one command.
As far as my tests went, GIMP is not really a solution and has a poor understanding of modern PSD files, and NodeJS happen to have a great new package that deals with the Photoshop format.
Instructions from the GitHub repo:
Install it:
npm install -g psd-cli
Convert myfile.psd
to a new myfile.png
:
psd myfile.psd
I hope you find this useful! The package is pretty new and other cool features will be added soon. Any feature requests and help with improving the code is appreciated :)