While I can't necessarily comment on features in progress, I can say that you should already be able to use Edge Inspect with Google Chrome to be able to view files locally. Are you looking specifically for integration with PhoneGap Build or just some way to see what it looks like on your devices without having to slap it up on a webserver?
Edge Inspect is great but I would like to use Edge to produce stand-alone offline apps for iOS, Android, etc. and an integration with PhoneGap would make the workflow a lot easier. Edge could create the needed project files and folder structure, then either use a locally available PhoneGap installation or upload the project to PhoneGap Build - a few seconds later you get apps ready to be installed on your favourite devices.