Top 14 side Racing 92 had high hopes of signing Read after talks during the All Blacks' European tour last November despite competition from an unnamed English club and Japan, French newspaper L'Equipe reported in January.
Read and his wife Bridget have three young children and they have always wanted to have an overseas experience together.
They want to have it before their children get too far into their schooling and 2020 is seen as the perfect time.
By that stage Read will be 34 and have completed his third World Cup – having been part of the victorious teams in 2011 and 2015.
He'll have played close to 50 tests as captain, been World Player of the Year in 2013, won Super Rugby titles with the Crusaders and played in a British Lions series.