I wonder what use they're thinking at all. Minix 3 is a step forward: were we to port Linux interfaces for udev, kevents, and such onto Minix, we could drop a Linux userland onto it wholesale, with systemd and all, and benefit from a core operating system which lends itself to drastic rearchitecting.
Consider that running Minix as an OS-level virtualizer--OpenVZ, LXC--is a trivial task, one which requires only providing a different network server and different security features (e.g. users and groups, and their flow through the file system driver and such), largely doable on the existing code base. You could even run Xen on top of Minix with a minor tweak.
Consider that Minix is a collection of services which may be extended by adding other services. It is interfaces and features, not tightly-bonded kernel code. The shape and form of the OS can be changed without commitment: to add services to handle Linux services is not to change Minix, for you may simply not use those services; you could instead add services to make Minix pretend to be OpenBSD. You could replace its threading model or scheduler by swapping out a service, providing a system that uses the advanced features of DragonflyBSD.
There, again, we see a step forward: DragonflyBSD, with its non-locking semaphores, its highly-efficient threading model, its ability to freeze an application and thaw it after a reboot, to checkpoint running applications--a feature Minix does not possess, but could simply by adding a new kernel service--and even to move applications between machines. Extending some of these things would be to bring the features of OpenMOSIX: check pointing and running an application on a different boot cycle or different machine brings the magic of scheduling applications across a cluster of machines acting as one.
Why, then, do we persist in creating these tinker toys, instead of extending, cannibalizing, or imitating those things which show real progress? Why has Minix not embraced the great strides forward made by Linux and integrated its interfaces so as to integrate its user space in distribution? Why has Linux not subsumed the threading model of Dragonfly BSD? Why has someone chosen to create an OS to no purpose, rather than to create a unified system carrying and integrating the lessons from all prior systems?