If you think you need to change CPU an motherboard now (or in the somewhat close future) it depends a little what budget is concerned. The 5820k will be more expensive than the regular i7 (about 100$ Or something) and then it comes how much memory and motherboard will cost. If they are very expensive it might not be worth buying an instead I would wait for broadwell but then the 5820k will have 6 cores, 12 threads and use ddr4 memory so it might be a better choice for the future.
It is up to you and what the budget will be. If haswell-E costs (motherboard, CPU and RAM) twice what a broadwell will cost I would maybe what. Would broadwell even have enthusiast hardware?