I doubt that the plant would move back unless Honda is getting serious .gov money to do so which is always possible but would normally be plastered everywhere for all to see.
They moved back to Japan because of the declining world market and needing work for the Japanese plants and workers, they moved lots of the high volume low cost Asian market motorcycle production that was being done in Japan to Thailand etc to accommodate moving the US and European production in Japan, they would of spent serious coin doing this they would need serious incentives to move it only 2 years later but as the global market has not really changed I cannot see they would have work for the Japanese workers to which the loyalty must lie as per local tradition.