Intel's next CPU model, Broadwell, may be out late this year. If they really get the performance they should out of their 14nm process, it will be a big win. But Broadwell will also require new motherboards, and it may not even be available for desktops initially. They may get a Haswell refresh this year, too. But I'm going to be conservative and believe Haswell will be the only high-end desktop processors for as much as a year. (AMD won't have anything new until well into next year.)
The only next-generation GPU technology on the radar is Maxwell. The first-generation Maxwells are promising, but they are not the real thing. nVidia has production problems with the 20nm Maxwells, and they may be available late this year at the earliest. (AMD will not have a new GPU generation out for a year or more. They are going with GCN and working to get 20nm parts built.)
So you can go with Haswell CPU, LGA 1150 motherboard, Kepler or GCN GPU now -- or bet on Intel and nVidia getting their production together by the end of the year, and get a Broadwell CPU, next-generation motherboard, Maxwell GPU then. The prices on the current hardware are not likely to be worse, so if you do not need the new hardware now, I would wait and look for the next generation by the end of the year. The worst you could do is end up with the same, which is still good.