so, does assad need to step down?

he does, actually. but, not for the reasons you think. i've been over this previously, but perhaps not here...

it's been clear for a while that the russians are going to succeed in clearing out the rebels, and there's not much that the americans can do to stop it short of sending in their own troops, which can't actually happen because the russians are sitting there, in the way. the americans have to fight this by proxy to avoid a direct conflict with the russians, and the russians are just about done eliminating these forces. let's skip the delusional bullshit and fast forward to a point where assad has reasonably secured the borders on the west of the country (as that is inevitable) and turns his focus entirely on isis. they're not going to win that over night, but let's say they do, and they're able to think about recreating their own borders.

well, then, they'd have to get into a hot war with the kurds. but, what happens after that?

it's very hard to believe that assad is going to stop once his borders are secured, and you have to get your head around a culture shock to really grasp that. there's all kinds of concepts of honour and retribution worked into this. as assad is aware that his primary enemies are the saudis and turks, who will continue to provide a joint existential threat even when the borders are re-secured, he will have no choice but to continue fighting them, even if we see a long period of peace and a subsequent military buildup or potential arms race.

if you leave assad in power, you are guaranteeing a hot war between iran and the saudis. assad cannot let it go. and, he will need iran's help.

while iran is no match for the saudis on paper, iraq is a potentially decisive wildcard - as is israel.

so, you have to get assad out. and, you have to get the whole alawite sect out, too, as they will not think any differently than him.

but, the idea that you're going to replace assad with one of these rebel groups, or some combination of them, is a non-starter.

fun fact: he actually wants to step down. he was trying to transition into a democracy. but, the saudis didn't like that. and, hence the armed rebels (there were never peaceful protests of any notable size...) moved in to prevent assad from transitioning the country into a secular democracy.

a transition needs to be done peacefully and orderly and needs to reflect the will of the syrian people, as expressed by the ballot box.

but, it needs to happen.

and, the russians don't disagree, either.