Although I share your frustration, good luck finding some of Nikon's more popular glass in stock at a reputable authorized dealers. Generally speaking, Canon's supply chain is superior to Nikon's. The grass is not always greener on the otherside.For me, as one who preordered back in February, this news is beyond inexcusable! Canon's photographic division must be completely inept. At this point, the ONLY thing keeping me with Canon is the TS-E 17mm. If Nikon comes out with a comparable lens, I'll switch in a heartbeat.
It usually happens for me, that the lane which I'm currently not driving moves faster. After I switch the other goes faster. But here you can be on two lanes at once, so why complaining? The story with Canon's preoders isn't such for the first time I suppose? What about the learning curve? As long as people will preorder so many months before the release, Canon has no reason to keep the announced dates. If people won't preorder once or two, then Canon for the third time will reconsider when to announce new stuff to appear on the shelves. I think, that preordering is like playing a roulette - if you are lucky, then you get one but if you have to wait, then you can blame only yourself.
People were waiting how many months for 1DX? How long after the first delivery was it available for anybody? Was it worth preordering? All those complaints about light leak in 5d3 I think came from people who preordered.
I really don't see any point in preordering AND complaining. If you preorder then don't complain, please...