As we notice that almost all the altcoins follow the price of bitcoin . I'm just wondering when they will become independent and don't follow the bitcoin price?
Probably never. I always think that these altcoins are just speculation tool. Unlike Bitcoin, they're not a real asset per se. So they will keep following major coin price, mostly Bitcoin.
When they stop copying the code of bitcoin and they stop copy everything that bitcoin does, that is when altcoins will begin to move independently of bitcoin and since most coins are just cheap copies of bitcoin then for the foreseeable future you are going to see those coins moving in the same direction, only the coins that have any kind of originality move independently from time to time from bitcoin.
Good answer, I agree. Most altcoins are just "selling" idea or concept that doesn't really has a real-world use.