Its become uncontrollable and windows can enable disabled services automatically and start from clean slate just like Mercury Man.
I am forced to update to FCU. For now I'm using WUMT to disable them and will move to RS4 once its in RTM branch.
I disagree. It's controllable if you use third-party program such as W10 Privacy and if you use the Group Policy Editor. W10 Privacy, among other things, blocks MS's telemetry servers through the hosts file. I just checked on my Group Policy Editor Cortana is still disabled.
Sticking with old software is not the solution. For example, DX12 is available only with W10. Also, you can't take full advantage of future CPU's such as Intel's i9 or higher versions of AMD's Ryzen unless you use W10. There are probably more examples.