If you upgrade to the R9 Nano, Fury X, or 980, you will see a definite increase in performance over your GTX 970. However, because you do not play games at 4k and the difference sits between 12-25%, I would wait on either the new NVidia or AMD cards to come out later this ear, and buy those.
After the recent price drop, the r9 nano sits at the same price as the GTX 980 ($500 U.S.) and is more powerful, so if you really do want to upgrade, buy the Nano at that price point.
Upgrading further, and you'll see that the 980ti is a better deal than the Fury X at it's price point of $650 U.S, and performs about 10-15% better in most games as well.
Your upgrade also should depend on the kind of work or games you play. If, for example, you do video editing on your computer, I think the upgrade might be a good idea. But if you're just upset with having to tune your settings to high instead of ultra to play at 60fps... I would wait.
Keep in mind that in some games, especially games that use NVidia Gameworks like the Witcher 3, the 970 and 980 will perform better than the r9 nano, but in others, such at Grand Theft Auto 5, the opposite is true.
All in all, I would just choose to wait until the new cards come out before upgrading, unless your job requires something more powerful or you have tons of cash lying around.
Just a side note, two 970's in SLI perform very similar to a 980ti, and you will probably save money going this route as well, but doing this will reduce your computer's upgrade ability, and some games and programs do not support SLI, leaving you with the power of only a single 970.