Details were posted on the official Gran Turismo website, and can be seen below.
・Your Driver Rating (DR) and Sportsmanship Rating (SR) status as of February 15 will be transferred to the new game. In some cases there may be some delay to the start date of these transfers.
・These transferred ratings will be applied upon the release of Gran Turismo 7.
・These transferred ratings will also be applied to the Test Season, an online championship planned after the release of Gran Turismo 7.
Gran Turismo 7 is scheduled for release on PS5 & PS4 on March 4, 2022.