There's no technical reason why it can't be done, as has been stated before.
Initially, the decision of lens IS vs IBIS (if it was even thought of then) was a no-brainer for Canon. Canon introduced it's first IS lens in 1995, well before DSLR's became mainstream and affordable. The 1.3MP Canon DCS-3 was released that year and cost roughly $9000 body-only. IS built into the lens could be used on emerging DSLR's as well as on the huge number of traditional film SLR's already out there. The first IBIS system (Minolta 7D) wasn't introduced until almost a decade later in 2004 (Not 2014 as stated above).
One main concern for Canon sticking with lens IS, is probably that IBIS seems to have it's limitations when being used with long telephoto lenses. There's only so far you can shift the sensor, after all. To overcome this, Olympus has "Synchronized IS" in it's new 300mm f/4 IS (600mm FF equiv) to allow the lens IS to work in sync with IBIS on the E-M1, E-M5 II, and PEN F for a claimed 6 stops of image stabilization. I believe Sony also has some sort of sync or uses lens IS for pitch/yaw and IBIS for roll, X and Y (turns off 2 of the 5 IBIS axes since the lens can do those better) with native OSS lenses from what I've read, but I'm far from a Sony expert and that may be completely wrong. Either way, in those cases of cooperative lens IS and IBIS you have the best of both worlds. I can't see Canon (or Nikon) sitting around and not adding IBIS to upcoming bodies for use with some sort of lens IS/IBIS sync system. Otherwise they'll just be left behind with inferior tech, which some would argue is already happening. I'm guessing the EOS-M line will be the guinea pig for Canon IBIS testing, and it'll eventually find its way into the DSLR lineup.