Trust me, as a driver developer, this has been causing me an immense amount of headaches, and Windows 10 is only part of the story.
But the blog entry has a key detail which nobody here seems to understand. Existing Drivers signed by a certificate that was issued prior to July 2015 will still be accepted by the kernel. What this means is that the new rollout is not going to cause the entire ecosystem of Windows legacy drivers to implode. If they were signed correctly for 64-bit Windows before, they will continue to work on Windows 10. Really, truly, I've tested this myself on preview editions of the Windows 10 AE
Where you get screwed is when a vendor needs to update a driver going forward. Then things get to be hairy. Logistically, signing became much harder, everything from obtaining a certificate to performing the actual signing. Pain. In. The. Ass.
Our company just released an update of our product just under the wire of when our legacy "get's a free pass" certificate expired so that we'd have some runway to incorporate the new driver signing nightmare into our tool chain. So we're good up until the next showstopper bug comes along, which fortunately is rare. You'll be able to use our latest release just fine on AE, even though it didn't get signed by Microsoft.