From What I heard, the Tohoku and Ryukyu people were discriminated and forced to speak standard japanese during prewar and during the war, is it possible for Tohoku, Hokkaido, Sakhalin and Ryukyu taken from Japan after World War II.
Possible? Sure, anything is possible. Likely is a different matter, especially Hokkaido, which is recognized as one of the "Home Islands". The same goes for the portions of Honshu that are populated by the Tohoku minority.
The Ryukyu's and Bonins were effectively taken from the Japanese until 1972 by the U.S. under the terms of the San Francisco Treaty that effectively ended the Pacific War (the Soviets/Russians & Japan never formalized a peace treaty, so the peace is de facto, not formal). Even today Okinawa has huge tracts of territory that are under long term lease by the U.S military, something that is a constant sore spot among the civilian population of the Island.
Sakhalin was, of course, divided between Japan and the USSR before WW II, but was ceded, along with the Kuriles, to the Soviets as part of the San Francisco treaty. The Ainu people , along with all other Japanese nationals, were forced off Sakhalin when the Soviets took full control, moving mainly to Hokkaido.