Yes, but a huge majority of the Canon buyers aren't even aware of the difference between Canon and Sony sensors.
But it's a bit hard to put a finger on a timeline when being late responding to the Sony sensor will actually end up being a bad decision. It isn't as easy as looking at some grumblings on a photo forum, or the view of some individual photographers. I think it's more important to try to look at the number of high-end photographers (the ones with a person cult around them, making others try to duplicate them) who switches system or who grows up and grows into a competing manufacturers system.
I agree with what you're saying, and yes.. they have to weigh the benefits of ROI. But there will come a time, when they will have to go with a new fab, or outsource. While initial outlay is high, the higher yields (eventually) due to using bigger wafers will pay off.


