I only read your excerpt, but the potential outcomes for Syria surely involve more than the al-Nusra, ISIL, or U.S. trained surrogates (moderates) leading Syria in the future. It seems a couple of other potential options are:

1. Syria as a we know it no longer exists, it breaks down into a number of real or pseudo-states.

2. Assad is replaced, but the Assyrian regime remains in power.

3. The Syrian military conducts a coup, and with help from Iran establishes a harsh military dictatorship (not a major deviation from where they're at now, but Assad would be gone).

I suspect there are other possible outcomes, to include Assad staying in power, because it is the lesser of the evils.