In Mitch's afterword, he reveals a statement that Morrie gave when asked if he believed in a higher power. He hadn't decided completely, but this strongly suggests that he has hope of one. He was an agnostic for most of his life, but maybe Morrie had a serious change of heart toward the end that he kept to himself. Certainly sounds possible.

Although this could be seen as a comment about spirituality as well, it tells us how much Morrie values his mind, his consciousness. If he could choose any way to live on he would want everything else in the universe to absorb him so that he can act as part of the whole big picture. His mind would no longer be limited to his body.