Be is much more like NT than OS/2 or classic Mac OS. Like NT: kernel written in C, portable, emphasis on multi-threading, robust against subsystem failures, shipped with a TCP/IP stack in the base OS. Be booted straight into the desktop but you could download software to give it a logon screen like NT4 and different users - the structures were already in place.

The current crop of operating systems may themselves be a temporary niche. The design of NT and unix are awash with single-host assumptions yet most use-cases are now networked. Consider the way that linux filesystem handles are specific to the host they are running on, rather than the grid of computers they run in. Yet we run word-processors in browsers, ssh to other host to dispatch jobs.

There is a gap for a system which has an API that feels like an operating system API, but which sits on top of a grid of computers, rather than a single host. The kernel/keeper acts as a resource-manager for CPUs and memory in the grid. Such systems exist in sophisticated companies but not in the mainstream. Apache Yarn is an example of a system headed in that direction.

Once such a system becomes mainstream, you don't need the kind of complex operating systems we have now. A viable OS would do far less - coordinate drivers, scheduler, TCP/IP stack.