Despite politically motivated arrests, alleged violent incursions and general animosity between the two, efforts are still being made to bring Hamas and Fatah together to once again form one Palestine. Despite Meshaal reportedly lying about how close a Palestinian reconciliation was, Saudi Arabia is now pushing for a personal meeting between Abu Mazen and Meshaal to discuss the Egyptian plan for reconciliation. Meshaal has also recently met with Syrian officials in Damascus about the reconciliation efforts. While presumably productive, a reconciliation between the secular Fatah and the Islamist Hamas would create several layers of difficulties for many regional and international players.
The Palestinian split provides a serious obstacle for the restarting of peace talks between Israel and Palestine. Hamas, which completely controls the Gaza strip, will certainly not accept any peace made with Israel if it is not involved in the negotiations. However, if Hamas and Fatah do come back together, peace talks with Israel become exponentially more difficult; apparently one of the major hurdles to Palestinian reconciliation is the right of Hamas to continue its armed struggled against Egypt.
The third complication here revolves around the west. Say, hypothetically, Fatah and Hamas were able to come to an agreement and that Hamas was willing to negotiate a peace with Israel, would the United States and the European Union be willing to work with a Hamas government? Currently, Israel, the US and the EU all categorize Hamas as a terrorist organization. The United States, who is currently pushing for the resumption of peace talks, refuses to talk with Hamas. Furthermore, Hamas is sponsored by Iran and Syria. Would the big guns in Iran and Syria allow Hamas to tone down its anti-Israel rhetoric and would they tolerate / keep supporting a Hamas that is talking with Israel (is accepting its statehood)?
There are many obstacles to a true Palestinian reconciliation and many more until a unified Palestinian government is able to truly sit down with Israel to negotiate peace. But if, by miracles, this happens, the legitimacy of Hamas in the Palestinian government would necessitate an shift in policy for the United States, Iran and Syria.