My take (others may have different perspectives/experience):
I agree that you will pay an early adopters' penalty for pre-orders and that you will be a beta-tester for bugs. Patience can be a virtue.
But, that said, don't expect the cost to drop significantly for the first 3-6 months after release, so if you can't wait longer than that, you are unlikely to save much by waiting.
The problems with new releases will generally be fixed quickly with firmware. Recalls and significant problems are rare. (I'm talking real problems, not the imaginary ones that circulate on the internet, for example: "I get noise when I underexpose by six stops! This camera is worthless!")
Here is my opinion. Take it only as an opinion:
1) It's great to support your local retailer. If you have a local retailer. But, for many of us living in small to mid-size cities in the U.S. the only local retailer we may have is Best Buy. Not that there is anything wrong with Best Buy, in fact, read on to see why you might want to purchase from them.
2) No guarantee that a local retailer will receive stock as soon as the large retailers. In fact, they may not get one in stock as quickly as the big boys.
3) I'm not fan of Amazon (Don't like their business practices, the way they treat their employees and the fact they don't pay local property taxes), but just because one person once had a problem with one product one time does not make a trend. So, take anything someone else says about their experience with Amazon with a big grain of salt.
4) I like to use other peoples' money. Since you won't be shopping for the best price, you can still shop for the best financing. I bought my 1DxII from Best Buy last year because I could use my Best Buy card and get 12 months interest free financing. I paid it off in about 10 months, so I got to use their money for free and never paid a cent in interest. In the meantime, I didn't have to take any money out of savings and was able to pay it off using my regular cash flow. I always take advantage of interest-free financing when it is available, even if I could pay cash, because I prefer to use their money, rather than deplete my savings. You just have to have the discipline to manage your money. Best Buy isn't the only option, most retailers offer interest-free plans through Pay Pal, which I also use.
5) Some people try to use retailers that don't collect sales taxes in their state. That's a personal choice, but you should know that most state's still expect you to pay a use tax (equal to the sales tax), so you owe the tax whether or not the retailer collects it. (Sure, you can be a tax cheat and not report the purchase, but that's a personal moral decision).
Finally, here is my personal "best practices" for Canon camera and lens pricing (varies significantly by product and this is meant only as a rough guide.)
1) The first thing you will see is "bundles" with worthless products like cheap filters, crappy camera bags, flimsy tripods and silly accessories like lens cap leashes. The big stores will attach an inflated value to the products and tell buyers they are "saving" $XXX dollars by getting the bundle free. You will still be paying full retail for the camera.
2) In a few months, Canon will likely offer a printer bundle rebate. You might be able to sell the printer for few bucks on eBay and reduce your net cost slightly, but is it really worth the trouble? Especially if it's one of the cheap printers. Check the eBay listings first to get a realistic idea of what you may net from selling the printer.
3) At some point in the first year, Canon will add the 6D II to its rebate program and you may save $100 or so. This is one way Canon adjusts their price to fit the market demand.
4) The first savings you are likely to see will be the Canon Price Watch Street Price program. This will be from an unnamed, but authorized dealer. The dealer can't advertise the price themselves because it violates MAP, but you will see a small discount initially -- maybe only $50.This usually take 3-6 months. Some of the retailers are Canadian and the lower price is a result of currency differences. Canon warranties cover both the U.S. and Canada, so no worries about that.
5) Eventually, the market will set the price and you will see the price settle in, usually for a few hundred or so below the original price at release. With the 6D the market price fell pretty rapidly. That was probably the result of the camera being overpriced in the first place. The 6DII seems like a much better value proposition, and I will be very surprised if it ever drops to the same level as the 6D. When it comes to pricing, the market always wins, but this can take up to a year and will fluctuate throughout the life of the product.
6) In about a year, the Canon refurbished store will start offering the camera at a discount. Once that happens, you will know the price has stabilized. Initially, the refurbished store price will likely be at or above the Canon Price Watch street price. But, eventually, the refurbished store will start offering limited time 10% or 15% off on refurbished prices. These are often a great bargain for lenses, but not always for cameras because street prices may actually be less or only slightly more.
So, what's a person to do? If you think you can wait six months, then waiting is probably prudent. If you know you will break down within a month or two of release, you might as well buy it right away and enjoy it. Just shop for the best financing option, or if you are lucky enough to have a local retailer, you can try to negotiate. I would not expect them to cut the price, but you might get a few freebies that you can actually use, instead of the junk you will get from a national retailer.