A mind that has achieved posthuman intelligence through psychosurgery is unlikely to think like a genetically improved Menton. Infomorphs may find less and less reason to remain in-step with the rest of transhumanity and increase the subjective speed of their simulations, out-thinking all others by virtue of speed. Forking is more likely to be experimented with by those in cyberbrains, if only due to convenience. The ability of biomorphs to heal and replicate still surpasses those of synths, could these be the building blocks of more social forms of intelligence? Each step allows for steps in new directions, directions other steps would not have revealed.
Eventually each train of development may come to its goal (if any), to local maximums too difficult to overcome, or to states of pleasing stability. In the deep future the self-improvement of individuals might give rise to lasting, identifiable types. There is not necessarily any reason to assume that "more advanced" types would erase those that came before: like in evolution, new forms can co-exist with the old in an ecosystem.