Merging.
We figure out what sort of stuff brains are and can make more of it in machine, but cannot scan it well. We make machines made of it which are non goal seeking but are hooked into a humans dopamine system in some way. Slowly we create higher and higher bandwidth connections between the two. It is treated as a semi- black box for understanding things, much like the motor cortex is treated as a black box for moving our bodies. This can lead to upload eventually.
Also related it may be theoretically better to have many agent with many goals to avoid getting stuck in local optima or with crazy ideas. See greater than linear speed up of parallel GAs.
Edit: To expand my second point. I don't think that groups of smaller intelligences will always beat out larger ones. Simply that I would expect that a mixed set of uploads will do better than a monoculture of clones. As the mixed set will consider different things important and explore different parts of concept space, and some will get lucky with fundamental break throughs. Clones won't do well if they all get obsessed with P vs NP and it is undecidable, for example.
I can conceive of AI designs that manage to keep diversity of concepts explored somehow, but I don't think it will come naturally from uploading.
Suppose we could look into the future of our Everett branch and pick out those sub-branches in which humanity and/or human/moral values have survived past the Singularity in some form. What would we see if we then went backwards in time and look at how that happened? Here's an attempt to answer that question, or in other words to enumerate the not completely disastrous Singularity scenarios that seem to have non-negligible probability. Note that the question I'm asking here is distinct from "In what direction should we try to nudge the future?" (which I think logically ought to come second).
Sorry if this is too cryptic or compressed. I'm writing this mostly for my own future reference, but perhaps it could be expanded more if there is interest. And of course I'd welcome any scenarios that may be missing from this list.