Thanks the SaveSelf and ReadKeys methods are new to me and look promising. Although, it seems quite awkward that after performing ReadKeys that one must delete the histogram object and then get it again.
At the moment the reading process is simply on the interpreter and I was able to update the histogram by simply calling TFile::Open again as shown below. What is the downside to this over ReadKeys?
root [0] TFile *_file0 = TFile::Open("test.root")
root [1] h->Draw()
root [2] TFile *_file0 = TFile::Open("test.root")
root [3] h->Draw() //Draws updated histogram