Nah, All Might is as good as dead, but maybe moreso "dead" like say Yami Yugi, a second self. Recall how Deku heard the voices of those who were All Might before him, that would suggest that the current All Might should inevitably become just another voice within Deku. I believe the final integration of All might's powers into Deku is for Deku to literally absorb All Might into himself and while the physical body of All Might may be dead, the mental/person my live as a thought within Deku's mind and may even act as a voice of reason to help out Deku.
However based on how the older All Might's were it seems more like the voices are just voices of inspiration and memories from the past so it's possible All might might just get lost like that and that's the truth he's hidden from Deku. That because of Deku, All Might will die, and it will be Deku's fault for becoming the new All might.