I am running a pair of 6870s and running 5760x1080 in eyefinity.
Some games I have to turn graphics down a bit.
But, anything that supports eyefinity plays acceptably well for me at that resolution in med or high settings (most games I can max out AA/AF and all options at that res).
6950s are a good bit faster vs my 6870s. If you are doing gaming at 2560x1600 or 2560x1440, or if you are doing it at any lower of resolution, then IMO it's not worthwhile to upgrade for a while yet.
If you happen to upgrade to a 4K display, or if you are running eyefinity with 3 or more monitors, then, I think you would see some significant gains in performance... (I'm on the fence here, since I suspect 1080p Oculus Rift or some other product will remove my desire for eyefinity... and I think my 6870s will be plenty fast for many years to come when it comes to gaming at 1080p.)