This seems like a good point on the surface, but since it takes only one outlier to dominate the universe (by Bostrom's train of thought), then it would have happened anyway. It's the law of smart for one, dumb for all. Assuming most life forms would decide to live minified, any life form not deciding so would have immense advantage to consume all untapped resources. Following this logic, and since any sufficiently advanced replicators would all be competing for the same space, the most overwhelming kind would take over all others.