Board Thread:Questions and Answers/@comment-13497263-20130726193119/@comment-11051098-20130918160353

Silias999 wrote: what if hes chosen ichigo as his replacement

After his Dangai-training in order to take down Aizen, Ichigo reached a level of power that even Aizen could not believe. At his peak at the time, even Aizen could not feel his reiatsu at all.

This was a temporary power-up, and we don't yet know the full extent of his powers now, but maybe his full potential is so great that the Soul King could actually choose him as his successor? Although that sounds way too wild to be true.

But - the Soul King could possess the ability to grant immortality to those he views as worthy, and if he/it could really consider Ichigo his successor, maybe he could make him immortal.