The thing is that with GPU there are new cards coming every 3 months or so, between two different manufacturers and all their refreshes. So OK you wait a few months and the new AMD cards come out, they will be expensive at the full MSRP, so you wait a month... then they announce a new Nvidia GPU, a refresh on the 700 series, a 760ti or 770 boost or whatever. 75% of the cost of the current GPU at 90% of the performance. So you wait a month for the price to go down, and AMD announces a refresh on HD8000 series. Then you wait another month, and the Nvidia 800 series comes. Then the H8000 refresh.
Just upgrade when you:
1. Have the need ( your card is underperforming for a new game ) 2. You also have the money ( don't "plan" on buying a card in a month or two when you can )
Just pull the trigger if you find a good deal. Never pay full MSRP for a card. If a brand new card comes out for $500, wait a month for a good $400-450 sale.
Thing is, I'm selling my old computer to a friend on the 31st, including the HD5870 I am currently using in my new computer. I can run off integrated until I get a new GPU, but October seems like a long wait. The potentially stronger than 780 performance for $550-600 sounds nice, but I might just get a 780 now so I don't have to wait 1-2 months.