I don't know about other people how many they actually are in figures who are using or holding Bitcoin in 2016. I will talk about me only as I am holding 6 Bitcoins and still whenever see possibility buy slowly slowly in cents. I hope I will b eable to collect couple of more before it reaches all time high in coming months.

I think 2 millions of persons at this moment... Just a supposition.

It's not a big number, and I'm supposing it, because we don't have a very big traffic on forum. Of course this is the best and biggest forum about crypto-currencies, but if the BTC was really being used in mass by world population, we would see more members here.

And I believe anyone who isn't a newbie on this world, have an account on Bitcoin Talk Forum, no?

I think some value between 1 million and 1.5 million seems to be a reasonable number, if you ask me. On the other hand, a value in the range of two million seems to be unrealistic, in my opinion, since Bitcoin is still in its early stages of expansion, with few merchants adopting the currency, hence few customers. This is likely to change, given the potential of it.

Other than Blockchain.info wallet, I think a site like Freebitco.in can give us a closer range of the number of Bitcoin users(at least the users who are actually interested in Bitcoin and deal with it or they wouldn't give a damn about the site, right?). The site has more than 3.35 Million registered members And I can assure you that this number is quite solid because the site is very restricted about multiple accounts. IF anyone tries to create another account he/she will get blocked on the registering page telling him/her "account is banned due to same IP Address used by an existing member" and if anyone uses a Proxy or VPN will also get blocked. I tested making another account on the site more than once and i failed. Unless changing IP Address(like using another computer or smartphone with a different internet connection than the one you currently have), you cannot make another account. So let's assume that all the 3.35 Million are real people, i can safely say that Bitcoin users/holders are between 3-5 Million users which is quite good! 

Well almost 50% user are keeping their money on hold because after july halving price fluctuation is quit low and many might had thought to sell after halving but unfortunately there was no price hike so they might had have kept their money on hold. But before halving there was quit instability in bitcoin price and I think more buying and selling took place in that period of time.

very many user , may be can see from wallet . because each user certainly wallet
may be >4 millions in the world

It's hard to tell because there are no existing data or figures,all experts can only predict or estimate,even I can't come out with a rough estimate because every users can have as many wallets as he desires,but hopefully one tool will come out to give us the right figure..

My guess is that the number of users is somewhere from 5 to 10 million users.
Bitcointalk.org is now closing up to have 1 million users.
A lot of bitcoin users start here, I suppose at least 10%. That would make a total number ot 10 million btc users.
If the percentege in my calculation goes up, the total number of users would decrease.