This morning updated my CentOS VM's to 6.7. Two out of the five exhibited network issues after the reboot, and after a second reboot they failed to boot entirely. The error reported was the root LVM partition was not found. I rebooted them using the prior kernel and everything came up as normal. These are production systems, so I can't do any testing, but I thought I would report here in case others are seeing this. The bad kernel version is vmlinuz-2.6.32-573.1.1.el6.x86_64 and I'm on ESXi 6.x. My plan is to use the prior kernel until the next newer one is released.
edit: I see at least one person reporting a similar failure on the CentOS forums. But he fails to mention what hypervisor he uses.
Probably the new kernel was not compiled with the same settings as the old one and thus some driver might be missing. Instead of compiled binary you could download sources for new kernel and compile it yourself, with options you need. As a good starting point you could use config of the running (old) kernel. It should be accessible in /proc, iirc /proc/config.gz...
Some people are claiming they forced a kernel reinstall to solve. I'm not sure what differs this kernel from the others aside from being accompanied by a HUGE number of other updates.