It's very hard to say, but I think probably 2 to max 3 million users.
Wallets don't say anything as there are services and companies who have hundreds of wallets with a balance.
Wait, what? it's way less than that, total users should be less than 100k people. There are total of around 220k unique Bitcoin addresses with a non-zero balance, and I personally owns about 20 addresses with balance, the average user should own at least 2 or more addresses with balance.
Good point, I have 6 addresses with balance.