This functionality isn't there at the moment, but, we'll have it in the next update of PS. For now, you would either change the scale of each export, or you can use Generator to rename your layers and export that way. If you are interested in giving us early feedback on what we are building for Export to enable multi-size assets, let me know.
Is there any updates on this? Designing for Android at the moment and the asset creation by hand is a pain to say the least.
I wrote this for Illustrator to export all artboards in a file for each Android resolutions; mdpi, hdpi, xhdpi, xxhdpi, xxxhdpi
1. "Export to..." will set a path for the current file.
2. Pressing "OK" will create a new root folder with active document name
3. Create a sub folder for each resolution (mdpi, hdpi, xhdpi, xxhdpi, xxxhdpi)
4. Export each artboard in file into each subfolder using the "scale" setting set in window.