Of course, the argument goes if you wait for the next best thing you'll wait forever. The problem is, nVidia - like Intel follows a "Tick-Tock" release cycle. Maxwell/900 Series is a "Tock" and while some bigger than usual improvements for a tock have been made (e.g. smaller die/better thermals, and CUDA optimization + DX12) it's not a major architectural change with massive improvements and new features.....
If you've gotten by three years with the 570's, and can tough it out one more year for Nvidia "Tick" cycle with Pascal, it might be more worth your cash....Not to say Maxwell/900 series isn't GREAT it is and an improvement of the 500 series for sure; but again if your cruising through games now, maybe take a breather.
This Maxwell release, lost Unified Virtual Memory to PASCAL (1000 series), and basically only has a die shrink (thermals), CUDA optimization and DX12.
Pascal will have all of the above PLUS unified virtual memory, stacked DRAM and NVlink. These are GAME CHANGING, large architecture defining changes. UVM (Unified Virtual Memory) and Stacked DRAM are the future and will bring MASSIVE performance improvements, and NVLInk sounds amazing for reducing the bottlenecks between CPU/GPU.