Sharon wont be able to return to power, that is basically certain. I mean unless there is absolutely no damage at all, I cant see him returning to power. As for his replacer, he or she will have a very hard time getting support from his or her own people and allies just due to the fact of the size of shoes they will have to fill. As for stabability in the region, Iran has made it pretty clear that they wont to wipe Israel off of the face of the planet, infact their rhetoric against Israel has been stepped up in the last few months. I have a feeling that this event with Sharon will only embolden Iran to try and preform a first strike situation while Israel is trying to find a replacement.