Assad has concluded he cannot win the war but hopes is that during the winter he can make life so hard enough for so many civilians that rebels will be forced to negotiate with him--though it should be obviously that the jihadi militant elements won't do so in any event.
I'd say the likely effect of the massacre on all other elements of the resistence wlll be to reinforce the psychological unthinkability of negotiations. All the opposition has to do is survive this winter of worse-than-Valley Forge hardships to triumph at they know it.
Survive until spring and Assad's chances of lasting until another winter become zero minus. Anti-Russian and anti-IRI feelings among Syrians becomes even more deeply embedded as they seek to enable Assad's murderous winter strategy. Hold out and Assad or those tied to him will never again be able to bomb Syria's cities, arrest and torture the people and or conduct Homs-style massacres. That threat eliminated, the Syrians will still have to deal with the jihadis before they have peace and can rebuild.
If there were ever a time when the US, Turkey and the West can do something to help the Syrians, reduce a jihadi near monopoly on aid and win over any public opinion, it is now. I'm not proposing a no-fly zone (at least not until all of the north has fallen into rebel hands) or a land invasion or giving anti-air to the rebels.
What I'd like to see is a a huge large humanitarian mission, escorted by armed protection, meaning primarily special force units equipped with anti-air missiles and anything else required to keep conveys and distribution areas safe. Perhaps drones can be used against any artillery-tank attacks. The humanitarian element would include food, fuel and anything else needed. We can't just let these people starve and freeze because it's in the interest of Assad, the IRI, Putin and the jihadis for that to occur.
I believe this plan also has the additional advantage of being politically palatable with people who live in western democracies, who don't want Iraq-style involvement but would like to do something more than at present. It also has the advantage of being hard for jihadis to counter wihout undermining themselves.