Currently three people are payed for working on Sugar: Marco (half-time, payed by Red Hat), Simon and me. We are in the process of hiring one more full-time developer, ideally based in Cambridge.
Marco maintains sugar-base, sugar-toolkit, sugar, artwork, hulahop, and maybe something else. Simon maintains Browse. I maintain the Journal and, as OLPC hasn't hired nobody for this, the datastore.
Technical decisions are taken in committee, with the participation of members from the community and other OLPC people.
The roadmap and strategy is given by Kim, who normally asks for the participation of several members of OLPC.
Last time I was told, Walter and Kim would work together and decide how the tech team could better answer the needs from pilots and deployments at every release.
This is not a formula for successfully implementing what amounts to a ground up re-imagining of how you interact with your computer. Sugar is comparable in scope to the iPhone OS. How many people do you think are working on that? This is really pretty close to the size of the SchoolTool team, and I know how fast we're able to move on a project that shares a number of characteristics with Sugar development. Two, or three or four developers is not enough people, and adding more people probably wouldn't help.