Valhalla is a divine realm outside of the context of the story and of Space-Time, so I seriously doubt that anything Jack did would even remotely effect it in the slightest.
The Warrior's soul is most likely still there, as Jack has been shown many times to be unable to effect the Gods and their Divine Artifacts.
If Jack could effect a divine realm just by defeating Aku and changing the future, then the power of the Gods doesn't really mean much in this story. Now does it?