I’m a big user of instragram and I don’t really see how you could implement such a feature to TubeBuddy outside of maybe giving TubeBuddy publishing rights to your Instagram (I don’t actually think that’s possible on instagrams end, I don’t think Instagram allows it) and even if they did allow you to say, automatically post thumbnails from YouTube onto instram, you’d have your thumbnails cropped on your gallery.
I do know Instagram allows you to push your posts to twitter, but I don’t think it’s possible to post direct to Instagram without going through the manual posting method.