As patents are a strong motivator for R&D investments, it happens, that they are against the market development. So I also hope here, that one day Canon, Nikon and Sony would exchange some of their patents when they will see, that it's harder and more expensive to offer a new real value to a final customer. If they can offer more for their customers in each new iteration of their products, it should be better for them, not worse. If changes introduced to new products don't justify significant money investment from the final customer, then the market shrinks as a whole as well.
Maybe it's some solution for them to fight against the market stagnation? In the end, when there is a financial crisis, they together, as big players on the DSLR market, fight together for money against other goods' producers.