Salaamun Alaykum,
It is generally viewed by Sunni scholars to be a fadila or virtue of Ali akin to other companions in the sense that it demonstrated his closeness to the Prophet as a dear friend and confidant. It is not interpreted by Sunni scholars to indicate that he was to succeed the Prophet. Of course the Shia school of thought differs with such an interpretation by looking at the words themselves as well as the implications therein in light of the Prophet comparing himself to Ali in terms of his guardianship or wilaya over the community. A good book in this regard is Shiism Imamate and Wilayat by Sayyid Muhammad Rizvi, it can be found on al-islam.org
regards and wa salaam
Sh.Vinay Khetia