With those benchmarks... damn. Not sure if I want to pull the trigger on a MSI 970 (and sell my 7950 while it has some value) while the Ubisoft offer is available or wait for this. I so want to play Witcher 3 at max (except MSAA or the like, SMAA is good enough these days) at 1080p.
1. Your 7950 is long passed the perfect time to sell it. For example, if you can sell it now for $120, in 12 months it's resale value might only fall $40 more to $80. Conversely, if 380X Fiji beats 980, that level of performance will fall from $550 to $400 or much more than the loss of value of your 7950. Alternatively at the $350 level there should be a GPU faster than the 970 by the time Witcher 3 launches. Put it this way an after-market 290 sells for $250 regularly but NV can charge a $100 premium for the 970 because its newer and has better perf/watt. That simply won't be possible once 200 series is replaced with an equally next gen AMD architecture.
2. You should never buy a graphics card for a game out months in advance. Witcher 3 has already been delayed for the 2nd time to May 19th, and it's not 100% that it will not be delayed again. If that's the key game you are upgrading for, then wait to buy a next gen card as close as possible to May 19th. We don't even know how 970/980 will stack up against 300 series. It could be AMD's 380X would own a 980 or 980 could beat 390X. It's impossible to say right now as W3 is an NV title.
I am in a very similar spot as you are. My 7970s together are probably worth $250-275 at most but I am willing lose $50-75 in their resale value over the next 6 months since instead of buying dual 980s for $1200, I'll probably be able to get even faster performance for $1000 by the time Witcher 3 comes out. That's why I don't see any point in upgrading now for Witcher 3.
In the meantime overclock your 7950 to 1.15-1.2Ghz as most can go that high. If that's still not fast enough for some odnthe games you play, you can always grab a 290/970 and not wait.