Rumor is yes, but from what I've read here:
* When you download a map, it's coded to a particular unit, so you can't just copy from a 730 to a 720. Somehow you'd have to fool the software into believing that your 720 was a model 730 with the same serial number or whatever characteristics they use to track that. It seems a few people have been able to accomplish this, but as it's technically piracy, don't expect a post here to describe the process in detail.
* TomTom has frequently stated that they don't intend the x30 features to work on a x20 (after all, the goal of a business is to make money). I half-expect them to release the v8 maps, and then handicap the following firmware release to disable the feature like they did with voice recognition on the 720's.