This is nonsense. If it were all about the bottom line, they wouldn't patch it at all, since developing and testing patches cost a lot of money. Deployment costs money, too, but that's cheaper.
The argument is that if you preorder, they'll have little incentive to patch, since they already have your money. But, on the other hand, if no one preorders the game, they'll also have little incentive to patch it, since it would be a waste of time and money to patch a game that people aren't even buying.
Now, if you preorder, they actually have incentive to make sure the release is good, since they can gauge the popularity of their game for potential sequels and stuff.
If nothing ever got patched people would stop buying the games, you can only push so far before customers start pushing back. If AC Unity had never been patched how many people would look forward to the next one? Or the one after that, etc. My point isn't that if you pre order there's no incentive to patch, my point is that when you pre order there's no incentive to fix the problems before launch, or to delay if necessary. Just throw it out there, get paid and fix it after the fact, IF AT ALL.
Mass Effect 2 (at least on PS3, don't know about other platforms), as an example, has a bug that can freeze your game during loading/auto saving. That bug was never fixed (at least I never found a record of it being fixed), never will be fixed. It just slipped through the cracks and never got patched out for whatever reason. Diablo 3 on console has a bug that makes your followers gear disappear that has yet to be fixed after being out for over a year. Something is always going to slip through the cracks, no game is perfect or ever will be, but these are REALLY bad bugs, the kind of thing that shouldn't make it to release.
As for pre orders as an incentive to fix these things before release... How is that? You've paid for it, the money might as well be in their hands. Why delay and risk losing that money when you can just fix it later maybe? The market hasn't shown much resistance, happens with loads of AAA games and sales are still profitable, millions of copies are still being sold and pre ordered. There's no incentive to fix it beforehand. If those pre orders aren't there they'll still fix problems with the game because it would still sell all those copies, no one is going to stop buying games at or around launch just because pre orders aren't a huge thing UNLESS they find out the game is broken trash while the other hot release that month actually works.