There is no
central governing
authority; instead, decisions are made
by consensus based on miners (or
nodes) signaling their approval for proposals, based on predetermined thresholds for passage that are embedded in the code.
Since Bitcoin is a decentralized system that is not controlled
by any
central authority, whether or not such an upgrade is deployed and adopted
by the network is determined
by several key decision - makers that must agree to the change: Bitcoin developers, economic Bitcoin
nodes, bitcoin - holding users, and bitcoin miners.