At the Help Center an article by Manton on Plug-in editing changes:

I’m so excited about all the activity around new plug-ins and themes. However, some of y’all have noticed that the behavior around plug-ins wasn’t really locked down enough before we rolled out these features. So I’ve been working on fixing that.

This week I’ll be updating with a few changes that I think will make developing and editing plug-ins (and overriding templates) more consistent. I want to document them here for plug-in developers to have a chance to chime in if they have any feedback