Hi Falak,
27 months ago, I received the same treatment (ATG/Cyclosporine) for SAA as your 9 year old friend/relative. Three months post-ATG, my level of improvement/counts were very similar to what you report, and I was still dependent upon red blood transfusions every 20-25 days.
As of last count, Hgb 13.6, Plt 163000, ANC 730 - and it is going on two years since I needed a blood transfusion. So, even though I only slowly in the first three months, I have improved a lot since then. I now work full time and have my life back. My energy levels have improved greatly. I go skiing, hiking, jogging. Tomorrow I will be running a 10k road race with my son.
But here is the tough part, aplastic anemia is a mysterious disorder, and the prognosis is uncertain. I am convinced my hospital and doctors are excellent, yet I have asked them many times the same sort of questions you are asking, and the basic answer is, "we very much wish we knew, but we don't". While we are fortunate to live in an age when there are good treatments for aplastic anemia, there is still so much hematologists are learning about this and other blood disorders.
Perhaps the person you are asking about will manifest even better recovery than I have had, or perhaps they will need additional treatment to keep improving. Perhaps I will continue to improve, or perhaps I will relapse and need further treatment.
There is certainly reason to be optimistic though:
1) The person you know is showing significant improvement, and three months is still relatively early in the process. Some slower responders still have an excellent recovery. Fighting this thing is a marathon, not a sprint.
2) The survival statistics for aplastic anemia, under both transplant and non-transplant treatments, are improving year over year.
3) Although the prognosis is uncertain, the longer a patient shows sustained improvement, the greater likelihood they will remain in good health without further problems from the disorder.
4) For patients who do not respond sufficiently to conventional treatment, new treatments such as eltrombopag are being developed which show promise.
5) Better understanding of human genetics will enable hematologists to customize treatments towards individuals, and ultimately more accurately answer the tyupe of all important question that you are asking "what treatment is best for the person I care about who is suffering, and when will they get better?".
Here is a wonderful organization for learning more about the latest treatments for aplastic anemia:
http://www.aamds.org/