I'm not sure if this is real or not (or even undocumented), but it looks like there is a green star on the map for set items. I saw it in a video from this thread.
This item changes, where can I find what are applied on old items, and what will roll only in new ones?
I'm pretty sure most of them are naturally incapable of being retroactive. The only one that might be off a quick scan is Stormshield because that's a special affix that could be changed in the database.
Not sure it's mentioned, but last PTR patch moonlight ward didn't retroactively get buffed..maybe bug, maybe not retroactively applied.. maybe they decided not to buff.
http://youtu.be/hclomZbWBQo?t=1m48s