As with other very-long-latency operations, RNG does not fit well as an opcode. There is also the problem that RNG algorithms may be expected to improve with time. Consequently we see such a box to be optional per-member, and attached through a different interface that is not fixed-latency like regular ops.
We do plan to provide a physical seed operation. This is not a RNG, but will provide a few bits of completely unpredictable entropy to start things off.