Playable at 60fps.
Would I need dual 290x or 970 cards
Max settings at 60fps?
You absolutely need a dual GPU configuration, either 290x in Crossfire or 970 in SLI.
I am chasing the very same thing you are. I would have two 290x Lightnings at the moment, but one is in processing for RMA at MSI. The second card still seems to be functioning properly, so the first card was truly just a bad board.
I was focused on the 970s initially, but the recent memory fiasco really tempered by desire for them. The 290x is not guaranteed to not disappoint in the end, as performance in Gameworks games can be iffy and I really really want The Witcher 3 to perform great, and GTA V for that matter but it is likely to not have really anything important from the Gameworks library.
You can also go a 295X2, which is what I would have preferred to do, however a few reasons prevented that from working out in the end.
If you aren't incredibly impatient like I tend to be, I advise you wait a tad. I doubt Nvidia will release anything affordable, but either that release will help encourage a price drop on the 980, or whatever AMD releases will. Ideally the AMD products will alone be worthwhile, but I can all but guarantee that the performance models of the 300 series will be priced over $550 or $600. AMD needs that income, and they need their cards to maintain a top-tier market presence. They tried it with the 200 series but they had to drop in price due to competition, at least once the cryptocurrency GPU mining rush died down due to ASICs taking over.
As long as they can compete in terms of performance with Nvidia's higher price cards, you won't see current 290X pricing for the next generation replacement, you'll see the $550 reference MSRP that it launched with. The MSI 290X Lightning was priced at $700! So you might take that into consideration too if budget is a concern.
Current cards might drop in price some more, but I actually sort of doubt they will drop much, they are outrageously low as it is, and has got to be hurting AMD's profits. They'll probably just cut production and let them dry up around the pricing they have today.
Hopefully, however, if a 390X is priced at $550-600, the typical high-end price that used to be normal, we might very well see a 390 or 380X at $350. It used to be the norm that the $350 price bracket had a phenomenal performance on its own, and a 380X should hopefully outperform a 290X, if ever so slightly.
However, due to the current lack of actual board leaks from either manufacturer, I highly doubt we will see the rumored spring releases. The original rumors were split between a March-April release and a June-July release, and I am expecting AMD to be at the latter. The HBM modules alone were rumored to only be shipping to manufacturers around this time in the year, so it would take to time to put them on the final packages and get those out to be put on PCBs.
To sum it up, if you are looking to buy today, I think the suggestion to go with a 290X Crossfire setup is the route you should be looking into. Check into the games you play and see how they perform compared to other options.
edit:
and I forgot to mention that, like lehtv said, you won't be able to achieve absolute max settings at 60fps for every game. There are certain things you can disable that will help dramatically and you'll have to experiment or determine which settings you would prefer toned down and which you still want to see at max.
The one thing that sucks about 3x1080p compared to UHD 4K is that 4K has a high enough pixel density to help minimize the visual need for AA, whereas 3x1080p still means a 1080p display pixel density, which definitely benefits from as much AA as you can add.