On the other hand, datacenters have become so large that a 1% performance improvement can amount to millions of dollars in hardware and energy savings, so the extra cost of a microkernel might not be very welcome outside consumer devices.
We did not yet have a big publicized hack of whole cloud infrastructure causing massive economic harm. When that happens (the buggy PC/Linux architecture running the world is ripe), more secure architectures will become commercially interesting despite the 1% performance penalty.
On the other hand, datacenters have become so large that a 1% performance improvement can amount to millions of dollars in hardware and energy savings, so the extra cost of a microkernel might not be very welcome outside consumer devices.