First of all Alex Smith is having a better season the Shaun Hill!!
In exactly the same amount of attempts and about the same amount of playing time.
Alex Smith 1035yds Hill 808
Smith 9 TD Hill 5TD
Smith 13 times sacked Hill 18 times
So there is no reason to go back to Shaun Hill which so many people are ok with.
Looking forward if Alex continues to progress from what he is doing now, I think there are bigger problems that need to be addressed on the team. This year might not be the year the 49ers go to the playoffs but you have to build on something, there is no reason to keep on rebuilding and starting from stratch