The effect isn't so much with vSphere but what the VMs and the guest OS and applications running inside the VMs would no longer see to be available.
Just an example, I am not saying that it will happen but quite possible:
Secure Key means the RDRAND instruction. That is used for generating a random number. Random numbers are important and widely used in cryptography. So a guest OS and/or application(s) running inside the VM might previously using RDRAND (because it was present) now have to fall back to use some other algorithm to generate random number. As it is no longer a single instruction (RDRAND) but a series of instructions, it could take longer and/or consume more CPU cycles whenever random number needs to be generated. Worst case, the quality of the randomness of the number might be affected. For example, if there is an application in a VM that generates one time passwords (OTPs), the quality/strength of the OTP might suffer without RDRAND (depending on the quality of the fallback algorithm).
