Not one to help Nvidia but those graphs show the 290x is that percentage SLOWER than a 980ti.
If in a theoretical game the 980ti gets 100fps and a 290x gets 71fps at 1080p, then the 290x is 29% SLOWER than a 980ti, but the 980ti is 40% FASTER than a 290x.
Humbug's numbers are more accurate and as such the Fiji would need to be >45% faster than a 290x to be beating 980 ti performance.
However I don't care about TX or 980ti performance, it's irrelevant. Value for the performance given is all I care about. the 980ti drastically increased that metric over the TX and the existing 980. If AMD again produce a card 10% slower but >10% cheaper, I'd upgrade to that over the comparative Nvidia card. If Nvidia have a card that offers better bang for buck than Fiji I'd likely wait for 14nm.
Not necessarily because I just don't want to support a company with terrible business practices, though that is a factor. But there is a level where I feel like I'm getting value for money over what I have. £550 to get 30-40% more performance over what I have now isn't going to do it for me. £400 for 30-40% is still pretty painful but more interesting. If there is again a £300-350 second tier card a la 5850/7950/290 pro, then that would be very interesting. £300-350 for what would probably be 25-30% more performance out of the box but probably more overclocking headroom and only 5-10% performance than a full on Fiji XT is where my money would probably go.