I have heard/read over the years that before his death, Stalin planned on deporting millions of Jews in the USSR to gulags, and that his death during the week of Purim prevented this from happening. Is there any historical evidence/basis to this story?
Stalin certainly started a round of anti-Semitic purges in the month before his death, notably the doctor's plot in which the Jewish physicians who treated himself and others within the Soviet leadership were accused of treason and trying to assassinate Soviet leaders. They were arrested in January 1953 and tortured in prison, this was followed by a wave of anti-Semitic and anti-Zionist publications in the Soviet media. Prior to this he had also grown suspicious of the prominent Soviet Jews of Zionism and possibly being more loyal to newly created Israel than to the Soviet Union. The subsequent round of arrests in 1948 included his foreign minister Molotov's Jewish wife Polina, who had greeted Golda Meir "too" warmly upon her visit to the Soviet Union a few years prior. He also purged the Jewish Anti-Fascist League, a Soviet organization which had turned into a sort of de facto Soviet ministry of Jewish affairs, staffed by Soviet Jews.
Right before his death he had also orchestrated the drafting of a letter, to be signed by prominent Soviet Jews, begging for the deportation of Jews away from major urban areas ostensibly to protect them from a new pogrom. He asked Lazar Kaganovich, the only Jew left in his inner circle, to sign the letter but Kaganovich was able to squirm out of it. Though he bitterly complained that Stalin would ask him to do this even though he had always struggled against Zionism.
Stalin was to die in March 1953, but yes, evidence points to that Stalin was initiating the first phase of another round of purges, this time anti-Semitic in nature.