How to change i2c address for mpu9250?
Might be a little late, but you can string more than two of these on one I2C bus, with a little ingenuity.

You connect the AD0 pin of each MPU to a different I/O pin of the processor, then take low the address of the one MPU you want to talk to.

Then that MPU has one address, all the others have the other address, and being slaves will not respond.

Provided you don't have more than one MPU selected at once, works a dream.