The Community Technology Preview (CTP) 3 of Visual Studio “14” released today that you can download as web package or iso package, or as Windows Azure virtual machine , introduces “high resolution icons in command bars, tool window toolbars (standard), and main menus when it is running greater than 100% DPI scaling”, according to the release notes.
This likely means that extensions should also provide high resolution images. Providing images for buttons and menus has always been tricky for add-ins due to transparency issues, magic colors (almost green, magenta, etc.), satellite dlls, etc. Fortunately VS 2010 solved most problems, only for VS 2012 to complicate things again with the dark theme and inverted colors.
I haven’t had the chance of playing with VS “14”, only to check that add-ins are gone, so packages are the only extensions that must provide those high resolution icons.