It really happened around the time of the war, cuz when Kakakshi died in the fight against Pain, he got reunited with his sensei and former team members. It was showed Rin hadnt aged at all since the Kakashi Gaiden chapters/episodes, which makes me thInk she died during war or a little bit later.
Edit:
He also said when he died that he could finally be reunited with the three and you will only say that when the person is dead and you know it for sure.