Depends on how much you want to spend. You can buy the current generation of flagships for a bargain right now, and probably won't notice any difference in performance vs the forthcoming flagships.
On the other hand, waiting will allow you a choice of going with, say a 1520 or 930, or paying double for a new flagship if you deem them worthy.
I'm enjoying my 830 for now, and will see what the new flagships offer... I'm concerned about design and branding with Nokia essentially out of the picture now (I know specs won't be an issue either with new flagships or current ones on Windows 10). If it has the hideous "Microsoft" branding, I'm going to have to pass. Just a Microsoft/Windows logo or the logo in conjunction with "Lumia" and I'll have to consider one of the new flagships.