Genuine question: Does this mean Btc is not so decentralized after all? Could they possibly decide one day to release an update to exercise ultimate control/power over btc?
It's certainly a point of trust, but ultimately it's the miners who decide how Bitcoin works. So far this has predominantly worked by them using software from bitcoin.org and upgrading it relatively frequently, but this would probably change very quickly once they stop thinking of the bitcoin.org developers as working in their interest.
There are alternative full-node implementations. A couple examples: