Hi here !
So, the captitalization of BTC reached 40B $ , this is nice but not huge at all compared to FIAT currencies.
My question is : with such a "low" amount of money, does the traders have real power over the Bitcoin price ? I always heared about the natural inflation, simply more demand etc... But don't you think that if a lot of early investors with huge amount of BTC could gather and have control over its price ? Or they are simply slave of the system like every one of us ?
I'm waiting for your toughts

Traders have all the control over bitcoin price.
Now, you and I can both be traders as long as we sell/buy bitcoin actively. There is no real "minimum" per se for you to be classified as a trader. But the more capital you hold, obviously the more influence you are going to have on the price.
Market capitalization rising is good, it does reduce manipulation to some extent. But the fact is that early adopters still hold bitcoin - so their share of the entire fiat market capitalization remains the same as their bitcoins has risen in price as well. So if they dump their coins, there will still be a major impact on the bitcoin value.
We all hate price fluctuation, but unfortunately that's what makes bitcoin special. It is completely out of the grip of governments.