(1) The board of commissioners of any noncharter county with a population of three hundred thousand or more may cause a ballot proposition to be submitted at a general election to the voters of the county authorizing the board of commissioners to be increased to five members.So, there is a way. The first way calls for us to grow to a population that, according to the Regional Planning Council (pdf file), we'll pass somewhere between ten and fifteen years from now.
(2) As an alternative procedure, a ballot proposition shall be submitted to the voters of a noncharter county authorizing the board of commissioners to be increased to five members, upon petition of the county voters equal to at least ten percent of the voters voting at the last county general election. At least twenty percent of the signatures on the petition shall come from each of the existing commissioner districts.
The other path, not from the commission itself, but from the citizens, can happen at any time.