Shatner really needs to accept the fact that he's not going to be the main character in a new Star Trek.
He might get a cameo (which he doesn't want), but even that would be pushing it. Resurrecting his character (something which has been done too often in Trek anyway) wouldn't make sense from a story point of view. Why did he age? Why does he seem so different? What makes him relevant enough to bring back for a new story with new characters? Even in the Trek universe, you can't just wave all of these questions away.