The phrase "natural successor" refers to a person who is expected or likely to take over a particular role or position because they have the right qualities, abilities, or experience needed for it. Full definition
During his campaign, Gonzalez presented himself as natural successor to Thompson, and promised to pursue a progressive agenda that will include an end to prosecuting minor offenses and bail reform. (patch.com)
The Sanchez replacement and the one that has really got Arsenal fans on their feet was Pierre - Emerick Aubameyang, who, with his pace and excitement is a much more natural successor to Sanchez. (justarsenal.com)
But should the Falcon Heavy prove successful, it will most likely be recognized as the natural successor to the Saturn V. (businessinsider.com)