The plan was for all operating systems on top of IBM's POWER/PPC hardware to be rehosted as "personalities" on top of the Workplace OS microkernel, but in the end, OS/2 was the only personality that saw any real work.
The Workplace OS would also have been used on Apple hardware as part of the abortive Taligent project.
(It also would have been used on x86 and other platforms, but they started with PPC)
In reality, in some ways we are there now. I'm wondering if we can say that the "workplace OS" can simply viewed as a hypervisor and the "personalities" that run on top it are simply VMs (perhaps being paravirtualized).