Far Cry 3 on PC is a whole new beast with far superior water effects, it looks so much better.
You can also put in so much more stuff in the editor - I really wish I had the chance to play it on Next Gen.
BUT
The Multiplayer and COOP side have so many issues that without some form of fix it would be pointless re-releasing.
Then if they do release an improved version on Next Gen I am sure that would cause so much hassle in forums as everyone playing FC3 on Last Gen would be bitter because the MP and COOP they played felt more like an unfinished BETA.