INTERPOL's current Secretary General, Ronald Noble, will serve in his position until 2015, when his third term as Secretary General ends.
INTERPOL's Executive Committee has chosen Juergen Stock as the candidate who is likely to become Noble's successor. His background and qualifications are summarized here, on INTERPOL's website.
The selection process is explained on INTERPOL's Structure and Governance page:
On 17 June 2014, Juergen Stock of Germany was selected by INTERPOL’s Executive Committee as its candidate to be the Organization’s next Secretary General.
The candidacy of Juergen Stock will be submitted to INTERPOL’s supreme governing body, the General Assembly, for endorsement when it meets in Monaco in November. If endorsed, he will assume office when current Secretary General Ronald K. Noble steps down in 2015.
Once approved, Stock would become the eighth Secretary General of INTERPOL, and the first from Germany. All of the previous Secretaries General were from member countries Austria, France, the United Kingdom, or the United States.