Gotrek ends up getting deified
His final adventure is called Godslayer. He actually punks a full-fledged deity and ends up ascending as the god of Slayers. He becomes the target for aspiring Slayers who seek a mighty doom. His only hope is that a Slayer takes his deific mantle from him. By force.
Gotrek's axe is one of the twin axes of the Dwarf god Grimnir
One of Grinmir's axes is in the possession of the Dwraf High King. The other is thought lost ages ago. Apart from explaining why it is so much more powerful than other mighty artifact weapons, when Gotrek and Felix had rules back in the 4th Edition of Warhammer Gotrek's axe had rules that were exactly the same as the Axe of Grimnir wielded by the High King - except that Gotrek's axe gained additional benefits against Chaos where the King's axe gained benefits against giants. This is pretty much confirmed in one of the final books by William King, when explaining where Gotrek found his weapon.
Gotrek's destiny is being shaped by Grimnir
Teclis theorizes that the axe is the work of a god and that Gotrek is its chosen instrument.