I think inheritance tax has huge downsides. Past a certain age, if you've done reasonably well, and are thus most likely to make a huge impact for the better in your latter working years, why do that most useful useful work if you can't pass it on?
Ultimately, people as a whole like to work. They dislike working under poor conditions or doing jobs that don't feel rewarding. A law like this would generate a lot of change, but I just don't see that change being disasterous given sufficient adjustment time.