Well, at least it will probably not be Jordan. King Abdullah has a 100 000 strong almost all hashemite army that will follow him to the abyss. Revolt in Jordan will not work, and that's the reason. There is some tension in Jordan over queen Ranja, who's Palestinian, but I don't think it'll amount to that much. A lot of hashemite tribes in on the east bank want her to stop playing politics, especially abroad. But other than that, I doubt that king Abdullahs regime is in any danger as of now. The king has appointed an old general as PM recently, but that's probably more of a statement than anything else.
Now, Syria, that's a more interesting possibility. However, I don't think that'll happen either. When I was in Syria, Bashir al Assad seemed quite popular. While people not speaking up against a dictator doesn't prove affection, there is always the hints you can look at. Like the fact that most people, but not all, keep a portrait of him. If nothing else, it indicated that no one forces you to stick up a portrait of him, but that a lot of people choose to. Unlike Egypt (and Jordan for that matter), Syria has still not decleared peace with Israel, which also helps the regime.
Lebanon, well.. who is there to rebell against? Everybody other than yourself? Meeh, if there's to be anything in Lebanon, there would probably be a civil war of sorts. But no one wants it. A couple of years ago, Hezbollah took control over Beirut, in the traditional coup d'etat way. They took the parliament, the police stations, communications etc. But they left them after a day. It was a demonstration of power, showing that they are able to do so. They knew, as the rest of Lebanon also know, that the only factor in Lebanon that could possibly rival them is the army. And the army is so divided it would probably fall apart if they tried to stop the Hezbollah. There's reason to ask what the army is really for, it can't secure internal stability, and if Israel decides to invade again, they aren't even close to being able to stop such an invasion. It's as useful as a chocholate tea pot.
Who's going to overthrow the Saudi regime? Most of them (the men, at least) lead nice, soft lives and are quite rich. Pretty much all physical work is done by cheap foreign labour (many from Pakistan), and if there's someone who could revolt, it would be the women. But the women can't win such a revolt, the religious police won't think twice before chopping of limbs if they start any funny-business.
Same sort of goes for the Gulf states. I guess my money might be on Iran, but I wouldn't put money on it (see what I did there?).