I've been wondering this ever since Silicon Labs (makers of Zigbee, competitor to Z-Wave) bought out Z-Wave for $240 million in December. I can't imagine the huge following of Z-Wave will be force migrated into the Zigbee network, too much adoption at this point. But to keep two separate systems might be unintuitive from a business perspective unless they are going to widen the gap between the two and differentiate between "enterprise" and "consumer" automation products.
Curious what others think.