With regards to the bit about plugins, will Apple make exceptions for their own software like Logic Pro X? I'm not entirely sure what the hosting/execution model is for AudioUnits and VSTs, what I do know is that many of them will never be updated to meet any new security requirements. I bet we're in for a few more years of terrible advice like "run this command that disables security in the Terminal, then reboot in order to use the product you bought."