I can't see the business case for not supporting distributed rendering of single frames: even with the optimization work to be done on the rendering engine there are still going to be rendering cases where those optimizations weather these be stability, speed or what have you are going to break down.
A frame manager is going to want too be assured I would think that detailed frames can be rendered singularly if required. As you know, some of the membership on these fora have produced images that have taken orders of weeks or some times months to render; it is clear that distributed rendering of single frames would be of grate benefit in these situations.
It would be nice if you could load the render only client onto rack based servers and/ or buy server based render nodes with it on already some companies sell software such as Maya installed on such server nodes, an interesting revenue stream to investigate.
Any way all this is for the future.
Regards to you.
Cyber-Angel