User blog comment:Wolf night10/The Final Getsuga Tenshou/@comment-28861328-20100610031838

I had a similar thought. What if Getsuga Tensho was a standard attack that all Zanpakuto possessed? That is a large guess considering we have only seen Ichigo and Isshin use it, but as I thought about it, I thought that it shouldn't be hard for any normal Shinigami to absorb reiryoku through their blades and release it as a shockwave.

Either that, or Ichigo and Isshin share Zangetsu. Both theories are radical, but it looks like we'll find out next chapter.

My final idea on this pertains to Getsuga itself. We've seen two "versions" of Getsuga Tensho. The normal version of Zangetsu's shikai, which is blue in color and can only be fired in one direction. Then we've seen the Bankai version, which is not only a different color, but it acts differently as well. It's path can be controlled, it's size can vary, and it can be kept inside Ichigo's blade to make the strike stronger. Not to mention the blast is vastly stronger in the Bankai version. Perhaps the "Final Getsuga Tensho" is a third version of Getsuga that will have additional upgrades and usage.

We'll have to wait and see.