America has long pressure that Assad must go. But Russia too has suggested that its support operation for the Syrian government does not mean that it supports Assad as a person as president. In this light there have been some suggestions that Russia's announcement of troop withdrawal might be a kind of pressure on Assad to look for a replacement.
At first sight there are good arguments for replacing Assad. The opposition doesn't trust him and considers him an inveterate liar. Corruption is widespread. His control over the army is weak: the most effective forces are the Tiger Forces who are known for their pilfering. In basic government too his track record is weak: half a year after the government conquered East Aleppo it still doesn't have water and electricity.
Yet this is tricky stuff. America's replacement in Afghanistan of Karzai by someone "more democratic" didn't turn out very well: the present government is divided and weak and losing territory to the Taliban. Karzai wasn't great, but his successors are definitely worse. During the Vietnam War too a replacement didn't turn out very well.
Dictators like Assad have also the means to sideline everyone who might be considered a suitable replacement. In that light I am a bit suspicious of the death of Zahreddine, the general who defended Deir Ezzor for several years and who had a great reputation for that.
The ideal scenario would be that Assad himself selected somebody in whom he truly believes and who is the type of hands-on strong leader that can rebuild Syria and overcome its factionalism.
On the other hand it might be wise not to be too obsessed with replacing Assad as it could blind one to other opportunities to improve the way Syria is governed.
According to Foreign Affairs Russia wants Syria to have some kind of power sharing like in Lebanon. I doubt whether that can work. The division between Christians, Sunni and Shiites in Lebanon is clearly marked and each of those groups has it own radicals and moderates. That is how Lebanon works and has worked for a very long time. But in Syria the main division is between moderate and radical Sunni's. Those groups are not clearly delineated. In fact they may be present in the same family. This is not a discussion between interest groups, it is a discussion about policy. And the solution is not power sharing but a gradual opening of the political discussion - while at the same time setting and guarding its limits.
It may be good to remember how the father of Syria's present president came to power - despite being from the Alawite minority. It had to do with the division of the Sunni commercial elite. That was divided between Damascus and Aleppo and a representative from a poor powerless minority seemed a good compromise candidate. Of course he acquired some real power. Things went really wrong with the Brotherhood uprising around 1980. This Saudi-sponsored uprising was focused on the Hama-Homs region where the Alawites traditionally live and where many still see them as the despised minority they were in the Ottoman era. In this respect you can compare this region to America's Deep South where many whites still look at blacks with the eyes of a slave holder.
You see the same dynamic still in the present uprising. Where much of the original protests focused on economic issues like corruption the focus soon shifted towards sectarian hatred of Alawites. The neighboring countries played an important role in that process: Saudi Arabia gave hate mongering clerics a podium and Erdogan openly declared that he wanted Syria to be ruled by a Sunni.
Without the harmful influence of its neighbors the logical development in Syria would be to go back to those business interests groups and to ask them to take the lead in charting how Syria should develop. However, the rekindled sectarian hatred won't make this any easier.
Postscript: yet another suspicious death. Mounir Darwish, a dissident who lived in government controlled Damascus was hit by a car on 11 January 2018 and then mysteriously died in hospital while he seemed to be recovering well.