That's a hard one to say.... Remember the powershot N, anounced January 7, still not in stores.....
I have seen everything from on sale the day it was anounced to lenses that were anounced 2 years ago and we still have not seen.
My guess would be about a month or two delay between announcement and release.
A month or two if we're lucky, I know about the Tsunami, production issues, etc. But Nikon has new equipment shipping almost immediately after they announce it. Canon, a much larger company with far greater resources can't seem to release anything on time. I just don't get it.
True ... but historically it has been the other way around i.e. Canon products were available at stores much faster than Nikon, but lately it seems to be the other way around ... if I am not wrong this seems to have started ever since they first announced the EF 200-400 lens.
I'm waiting for the 70D release because Canon MUST have an all new sensor by now. I can't imagine them going with the same 18MP sensor they've been using since 09, but I've been wrong before....
5D MK III, 16-35/2.8 L II, 24-70/2.8 VC, 24-105/4 L IS, 70-200/2.8 L IS II, 100/2.8 L IS, 40/2.8, 50/1.4, 85/1.8, 150-500 OS, 600EX-RTx2, ST-E3-RT, Rokinon 24/3.5 T-S, D7100+18-300 VR, YN568EX, 055CXPRO4+468MGRC2, 190CXPRO4+322RC2, Gorillapod Focus+496RC2, CamRanger, B+W filters, Konova K3/31.5 etc