I believe this is one of the main reasons HT docs recommend that you get on Propecia immediately prior to HT. Propecia is pretty effective at curtailing hair loss from the back third of the head (i.e., in front of the crown back). Since most people have enough donor hair to support multiple transplants, if the hair loss continues you can have a 2nd or 3rd transplant as you age. If done right, I believe the hair loss can still look somewhat natural (albeit different) even if hair loss progresses towards the crown.
My HT surgeon said that he normally has a 90%+ success rate on grafts. I haven't had a problem with mine. I'm sure there is the unique case where a patient has some medical issues that would cause a less than optimal result but I would find it difficult to believe that a surgeon who takes the necessary methodology and process during a HT wouldn't have a very high success rate. I think if you go with a reputable surgeon than your probability of a failure is almost negligible.
I'm a citizen of US. I wouldn't feel too apprehensive going to Canada for a HT. I would, however, feel apprehensive going to India.