Thomson (30) is believed to have accepted a contract to play for a club side in Japan, but will not play in the land of the rising sun until the start of the 2013-14 season.
What he will do until then remains a mystery but he is not expected to be named in any Super 15 squad today.
He was linked with a move to the Blues earlier in the season and his dithering around led to the Highlanders spending their money on other players and filling its playing roster.
The rangy loose forward was named in the All Black end-of-year touring squad on Monday with All Black coach Steve Hansen saying he was picked on form.
Hansen said he did not know what Thomson was doing next year but that had no impact on his selection.
Highlanders coach Jamie Joseph was also in the dark about what team Thomson would play for next year.
Thomson could conceivably play Super 15 rugby next season, as it is played before the season kicks off in Japan.
But his body has taken a battering in the past few years and it may be wise to take a break of a few months to extend his career.
There may also be doubts from Super 15 teams over his total commitment for the season if he has a lucrative contract at a Japanese club lined up.
His departure from the Highlanders is a blow to a side which has assembled an impressive-looking squad.
After he has played so well for the Highlanders for the past five years, it is a shame Thomson is moving on when he would have had the quality of players around him to make the side competitive.
