Depends on what you find as an "acceptible framerate". If your monitors refresh rate is 60hz then you don't need more than 60fps, and in that case no, one gtx 780 won't be able to max out all games 60fps in 1440p. However i bet you could play battlelfield 4 on medium-high and keep 60fps for most of the time in 1440p.
Also you could try overclocking your GPU.