I agree that the ownership of natural resources would still matter. I don't think that concentrated oligarchy is the probable outcome, though. If robots do everything, trying to prevent copies is like trying to prevent copyright infringement. It's the clanking, macroscopic equivalent of having a replicator. It's as easy to make weapons as to make appliances. I can see things spiraling out of control to the point where e.g. routine civilian air travel shuts down, following the wide availability of MANPADS, and nuclear proliferation runs amok, but I don't see a stable equilibrium that ends with secure oligarchies. There are too many rival oligarchies in the world for them to coordinate on the problem of keeping do-everything robots locked down in the interests of their own safety. There will be defectors.

with a self replicating robot you can build an army of robots that can build rockets that can take self replicating robots to asteroids that can be turned into goods and habitats by the robots.