If the miners refuse to switch, and the majority of the private node holders refuse to switch, then the service providers who you mentioned above can go off on what ever fork they want, they still wont have control of the network.
Unless the majority of each section decide to make the change and, in doing so, force that change on everyone ele, then it wont happen.
Let’s say, as per your example, the main service providers make the switch, but the miners don’t. Fine, most wallets run by third parties are now on the new network. And it can be 51% attacked and screwed with by anyone with an antminer U2.
Not so cool.
We all depend on each other in this ecosystem, so really, there has to be a majority consensus across all the different sections.
Democracy is a messy beast, for sure.