Sherrington, who is not thought to have another job to go to, has agreed not to leave the company until a successor is found.
Headhunters are understood to have been briefed to find his replacement.
Sherrington joined the company, then known as South African Breweries, in July 2002, and was given the task of rebranding it following its £3.8bn acquisition of Miller.
He has been responsible for overhauling the Miller brand and relaunching Peroni as a global beer brand, backed by a multimillion-pound marketing spend.
An SABMiller spokesman said Sherrington's three-year contract ended last August and had been renewed "at the company's request for a further 12 months". He is expected to leave before August.
Prior to joining SABMiller, Sherrington worked in senior marketing roles at Unilever before leaving to launch marketing consultancy Added Value.
He is one of only 12 marketers on the board of FTSE 100 companies, and his successor is expected to have a similarly high profile.
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