It all depends what you have and if you can wait! Really if you are playing at 1080P then there is nothing the GTX780 can not handle.
Well, I currently have a very old gpu but I was planning to use at 1920x1200 and not only gaming.
I am planning to do 3dsmax vray rendering which requires cuda.
Nvidia cuda roadmap puts maxwell way higher than the Kepler based gpu's so wondering if its worth the wait (also thinking about lowering current prices?)