This has been brought up before and I don't think anyone on the staff is knowledgeable on programming for Android. All Android phones are different and require plenty of bug testing, which would be difficult with a limited staff. And then if an Android app comes out the iphone people would want one, and programming for iphone and getting it store-legal is an incredibly arduous and expensive process (basically impossible for such a small site).
The site is already mostly mobile friendly, so this likely will never be considered.
Mass uploading is already a Premium feature.