What's probably going to happen is more isolation. SGX is a target for these vulnerabilities because it's a separate mode of the same processor core which runs

What's probably going to happen is more isolation. SGX is a target for these vulnerabilities because it's a separate mode of the same processor core which runs normal software; were it on a dedicated core, it wouldn't be vulnerable. In the same way, the kernel can be attacked by user processes (and processes can attack each other) only because they share the same core. So I'd expect to see for instance the kernel running on a set of cores separate from user software (probably using a ring buffer interface for most system calls, like io_uring), and the hardware state being totally flushed when switching a core to another process.