Sommer joined Bayern last winter when the team needed a speedy replacement for the ailing Manuel Neuer.
The 34-year-old has started every game for the defending champions since joining from Borussia Mönchengladbach.
However, the goalkeeper and the club have agreed that if Neuer returns in the summer, he will take over as number one and the Swiss international can depart during the same transfer window.
With the European Championships approaching, Sommer would be wise to seek regular football elsewhere right soon.
He cannot afford to wait on the bench at Bayern, as both Gregor Kobel (Borussia Dortmund) and Jonas Omlin (Gladbach) will continue to play for their respective clubs.
Manchester United has been interested in Sommer since his days at Gladbach.
The Red Devils have long been interested in him as a potential replacement or rival for David de Gea.