Ha-aretz discusses the question of "what if Rabin had lived?" The author quotes a Netanyahu ally, who observes:

Had Rabin lived, he said, he would "most likely" have lost the elections to Netanyahu, who had a big lead in the opinion polls - even before the wave of suicide bombings in March 1996. "The Labor Party would then most likely have replaced Rabin with Ehud Barak and history would have played out the way it has."
Elitzur said the claim by many on the left that "the world would have been fundamentally different" had Rabin not been killed, was an attempt by the supporters of the Oslo accords to explain away the great failure of the process which Rabin led. "But in the end I don't think history would have been different. Yigal Amir did not change Oslo. The failure of Oslo was not the result of Rabin's absence."

There is much truth in those observations. Netanyahu led Rabin by 22 points in January 1995 and by 23 points in April 1995. Rabin's assassination gave Shimon Peres, by contrast, a big lead in the polls. Having been in Israel at the time, I can attest to the fact tha there was never less opposition to the peace process than in the aftermath of Rabin's murder. What changed the picture was an orgy of bus-bombings by Hamas. (A reading of the list will show that there were a large number of such bombings when Rabin was alive, as well - a large contributing factor to his low poll numbers.)
More importantly, ascribing the failure of the peace process to Rabin's murder ignores the proximate cause of the war of the last two years: the refusal of the Palestinians to compromise on the demands which they entered the Oslo process, most notably the "right of return." That final phase of bargaining would have arrived regardless of whether Rabin had lived, and I haven't seen a good argument that Rabin would have made any difference in the Palestinians' refusal to cross that line.
It is a natural tendency to assume that the most dramatic events were the most pivotal events, as well. But that is not always the case.