There are two groups who want the Assad regime in Syria delivered a mortal blow: the Israelis because Syria is acting as a conduit for weapons from Iran to Hezbollah which is conducting terrorist operations on Israel's northern border, and Saudi Arabia because the Syrian regime is Shia and the Saudis are Sunni and there is long enmity between Saudi and Iran.
Does anyone really believe that the US government will be able to resist the twin pressures of Saudi oil money and the Jewish lobby? Of course not.
And will the UK be able to resist the call to arms from the USA? Again, this is not likely - the UK government has too much to lose if we piss off the Americans. They might stop sub-contracting spying work to us!
So Assad, your butt is toast!
The net result of Western intervention will be to even up the relative powers of the regime and the rebels. This will prolong the conflict, cause more deaths than would otherwise have happened and eventually bring about a Western-hating Muslim Brotherhood government in Syria. Job done!