Iran and Iraq are the only dominately Shiite nations in the middle east the rest are predominately Sunni, including Syria. Likewise, Syria is a relatively secular nation, in the same way Iraq was, Iran is a Theocracy. Therefore, Iran and Syria aren't exactly prime material for bosum buddies. Lebanon is an extremely weak state, the government hardly controls its own territory, if at all. The idea of Lebanon invading another country in any meaningful way is impossible. Meanwhile, Israel's defensive forces and air power have been demonstrated to be far superior to other countries in the region. I doubt we'll see a large scale war erupt between Iran, Syria or Israel. Most likely we'll see a continuation of funding for groups like Hezbollah and suicide attacks on relatively soft targets.

Now escalation to the point where a war between the United States and Iran seem inevitable is possible. But thats a war we don't really want to enter, the armed forces are just far to stressed from the war in Iraq as it is. Entering into another large scale conflict just isn't currently sustainable.