He might be able to strip the title of any unentailed property and leave that to someone else. But the title and the entailed property do not belong to the duke (or other peer), but are held in trust for his descendants.
inheritance
The right and the wrong side of the blanket
The British royal family can trace its ancestry back to the kings of Wessex and Kent, at least 1300 years, though it gets a bit murky beyond that. The family tree on this site links both the English line and the Scottish line through a descendant of Alfred the Great. Often through the female line, and sometimes through collateral lines that have long been separated from the main tree. But still.