It is hard to look into the future but I think currently Nvidia's 780 is the best card when looking at price to performance ratio. A lot of AMD's cards are getting jacked up due to coin mining and are highly inflated. Right now you'll' find the 780 cheaper than the 290x and the 780 seems to perform better.
As far as the future: Nvidia will be releasing Maxwell soon and the 790 sooner. Things can always change on a dime.
I'd agree that 780 is primo right now, especially at the price. But Maxwell is also coming soon, which means either better card, or, price drops on existing ones possibly. Also, the 780ti is a screaming deamon of a card, hundreds of $ more but id say best single card out there. The gtx 770 is also a great card, especially considering the price. Otherwise, I guess it depends on what you have now as far as gpu, to have an idea if an upgrade is worth it. If you have like a 7870 then a 770 would only be a small upgrade and nto really worth it. Plus a card like that also should play games just fine so id def recommend waiting for new releases. If your card is like a 650 / ti, then a 770 is closer to a realistic upgrade.
Plus we would also need to know your budget. I can give you good deals on a 650ti a 7870 a 770 a 780 a 780ti, or anything. But I don't know what your looking at, or what the upgrade is going to be.