The "castor" wheels would have to be powered drive wheels, bulky and complex. Also the diameter of the brush cylinder and front bumper place the acting center of the brush where it touches the floor and inch or so away from the wall. The geometry...
This software update publicly admits Neato navigation can be improved, so it would be peculiar not to release this software for XV models over the next few months, marketing wise. A possible issue is longer run time to clean the same area, with extra time backing up, and the Kobold having bigger batteries. Doesn't look enough to make more than a 10 per cent decrease in area covered at most to me, a few seconds at each corner, maybe a dozen in a convoluted room, and probably less.
Software releases get some notice in the specialized press covering these things, so there is some gain from release at the most opportune time for seasonal advertising. Neato doesn't advertise to speak of, with such small volume. Had a chance conversation with a customer in Radio Shack curious about robots for a large house, and had never heard of it, appreciated the news. The defunct listing in Hammacher
was at least good advertising.