It could beonly a matter of time. Any company withholding useful technology from their equipment do so at their own detriment.
Then again who's to say that the big two Canon and Nikon haven't signed a nice little document to the benefit of both companies - Not to implement IS on the body. At least for a specified time -say next 10 years. Would make a lot of sense. Cos at the moment the inclusion of IS on Minolta and even if introduced by Olympus and anotherSLR manufacturer, its not going to effect the established Nikon and Canon market that much.
However if either Nikon of Canon introduced this feature the other would also have to follow suit. At the moment it suits boths companies to sell the technology they have developed and have paid forand have working on their lenses.
Now when, and I do mean when ... sony start to put this on all the pro-sumer cameras, its more likely that the pressure of the technology "established norm" will pressurize thelikes of Canon and Nikonto put it on also...... but when.... who knows.