It is possible to get the precise number of bitcoin users if ever all the users are using a bitcoin wallet services that are collecting some personal information from a certain user for verification purposes such as IDs or bank account or whatsoever but this case wouldn't be in favor of the users .
Really? I guess not, it is impossible to see the exact volume of users of bitcoin in the way you are suggesting. There are a lot of bitcoin wallet out there and some uses off line wallet which is not I guess counted on what you are suggesting.
And for sure an individual can make a multiple bitcoin wallet account so how can you get precise number there? Its almost an impossible query to sort out as we are highly unlike to get the accurate results.
Yes its impossible to predict the exact number of users using bitcoins as most of the users have multiple wallets to store their bitcoins so in that case it will be very hard to find the exact percentage of users involved in bitcoins.