It very well could be 3 different people that have solved the last few keys.
Bitcoin isn't worth $3000 anymore like it was at the beginning of the year. Its almost $13K so the person who found the 1 BTC made alot of money.
Most people who visit this thread could be lurkers and they can have more knowledge than us and hardware. So there could be about a dozen or so people who are trying to find the remaining private keys. Its definitely worth the time.
Or could be that those who found the private keys are individuals in the same group with the owner of the puzzle.
I'll believe something else when I will find one of the private keys and I will be able to spend it.