John Paul II visited Lebanon in 1997. The situation has changed somewhat since then.
I have even read recent speculation that Syria’s Assad has calculated that while he cannot maintain rule over the majority of Sunni dominated Syria, his army is powerful enough to completely dominate western Alawite (Shiite) Syria, from the southern border through the Mediterranean coast.
However, this is dependent on Hezbollah splitting off eastern Lebanon to join with western Syria and form a new, Shiite dominated nation. This would effectively double the size of his army at the same time, and would be fully supported by Iran.
The Lebanese are ill equipped to prevent this, and might even accept it in that their government is stymied by Hezbollah, yet they have no effective controls over Hezbollah dominated territory. They would finally be able to rule a smaller Lebanon.
And this is just one scenario of a very complex situation.
By far, though, the biggest threat to the Pope would be assassination by bombing, for which there are endless experts in the region, Lebanese and foreign, government sponsored and independent.
And Iran has been sending dozens of assassination teams to every corner of the world, fortunately most of whom are compromised or at least incompetent. Large contingents of their parent organization, al-Quds, are currently in Syria aiding Assad with their willingness to slaughter Syrian women and children.
Balance all of this with what might be gained from a Papal visit to Lebanon.
You might be correct in your assessment, however, if there were to be an assassination attempt on the Pope I would bet my life that it would be perpetrated by Sunni muslims and certainly not hezbollah or syria. The closest allies of the Alawites are the christians in Syria, Assad would not damage his christian support because that would spell his doom. Hezbollah would not attempt a similar move because they have nothing to gain and are very organised in keeping their members in check.
The threat comes from a lone gunman type scenario in which case a sunni muslim extremist fits the bill perfectly. That being said muslims in lebanon know not to target christians, hezbollah didnt even try to enter christian areas of beirut when they did their little takeover and retreat, because they knew it would escalate, the christian civilians are very well equipped to take care of problems themselves and hezbollah know this. Last time a church was attacked by palestinians, the christians ignited a civil war and did quite well eespecially since their only ally for part of the time was israel, with the rest of the world looking neutral and all arab countries financing muslim militias to murder christians.