Not sure if anybody is going for the previous generation versions but it looks like they're upgraded for free - before January 15.
http://ca.ign.com/articles/2014/09/0...ource=facebook
Purchasing a last-generation version of Destiny digitally will get you the new generation version for free.
Activision and Bungie announced a digital upgrade program for Destiny, which will let players who purchase a digital copy on PlayStation 3 or Xbox 360 upgrade to PlayStation 4 or Xbox One, respectively. That also includes the Guardian Edition and Expansion Pass, as long as it's kept within the same "console family."