I think the amount of dormant coins is even much worse than this 7 million, if you take into consideration that the big-users have multiple addresses and move from one address to another occasionally - let's call this "sleep-walking"; it is something I noticed when looking at the top 100 addresses.
In your sleep-walking case, the bitcoin should not be considered dormant. The definition of dormancy is the time duration since last sent.
Also, I believe the largest addresses are associated with some service provider, such as coinbase.