At its WinHEC hardware conference in Shenzhen, China, Microsoft talked about the hardware requirements for Windows 10. The precise final specs are not available yet, so all this is somewhat subject to change, but right now, Microsoft says that the switch to allow Secure Boot to be turned off is now optional. Hardware can be Designed for Windows 10 and can offer no way to opt out of the Secure Boot lock down.
The presentation is silent on whether OEMS can or should provide support for adding custom certificates.
Read more at ArsTechnica.