No, no one ever answered this one. I'd say that the emphasis is on the Mayflower passengers themselves, but certainly the next couple generations, and perhaps also their ancestry, could also be in the scope of this group.
In the Acadian group (which deals with the same sort of time period as this group), I usually do the first settlers, plus their children and grandchildren. By that time, you're getting into people who are less than 300 years old, so it's harder to really do large-scale collaboration on them. Also, there tend to be less duplicates as you get to more recent ancestors, so most of the work will probably be in the first generation or two, anyway.
~Lianne