I guess it depends how patient you want to be. Also, it depends on your budget and needs. Are you trying to buy the best GPU you possibly can for under $1000 dollars (no Titan or 690/7990 etc.)? If so, then waiting for Maxwell might be worth your while. If your budget can't exceed the price of a GTX 780 Ti, then I doubt you'd be benefited by waiting for the new architecture.
As for Broadwell, at the very least buy a Z97 motherboard, no matter when you buy your computer. I can't say for certain, but Broadwell will most likely bring incredible efficiency and a sizable boost in IGPU power, however I doubt sheer processing power will be much different from Haswell. Sure, broadwell has a large last level cache (LLC), but I really can't say how much that will improve performance over Haswell. I doubt it will be worth the price premium of a new product, but only time will tell!
I would at least wait for the Devil's Canyon releases before buying a CPU.
I'm looking at buying the ASUS Z97 Pro.
I have the budget to get any GPU under $1000 so I probably will.