In 1975 Fred Brooks wrote that adding people to a late project makes it later. The arithmetic is simple: every new person adds lines of communication, and n people have n(n-1)/2 of them. Fifty years on, most of what we call project management is the paperwork of that arithmetic: handovers, interfaces, meetings, status reports. We manage the space between people because we could never build things inside one person.
That is changing. One person with capable software already ships what used to need a small team. By 2040 the size of a project will no longer be limited by labor. It will be limited by how much one person can understand and answer for.
Labor stops being the resource
Hours become elastic. A thousand of them can be bought overnight. Resource histograms, leveling and staffing plans were built for scarce labor, and they lose their subject. What stays scarce is the ability to understand a thing well enough to sign for it. A bridge can be drafted in a day. Someone still has to be the person who knows why it stands.
Interfaces get designed away
If the cost is coordination, the clever move is to need less of it. Large projects will be cut along new lines: not by trade or department, but by what one head can own from end to end. Fewer handovers, bigger slices of responsibility, each owner with a fleet of agents. The work breakdown structure becomes an ownership map. It stops asking "what are the tasks?" and asks "who can hold this?"
The schedule of attention
The critical path will run through people: a few owners and their capacity to review, decide and say "this is right." The real plan becomes a calendar of attention. Where do the scarce hours of human judgment go this week, and what must never be reviewed by a tired person at six in the evening?
Most failures will not be late work. They will be unchecked work: fluent, plausible and wrong.
The old profession managed the space between people. The next one manages how much a person can truly answer for, and keeps every project no bigger than that. Great things will still be built by many, but by many who each understand all of their part.