As the crisis in Syria intensifies and Bashar al-Assad's hold on power starts to unravel, concerns are mounting over what may come next for the beleaguered nation.

Some foresee bloody sectarian strife or a descent into militia rule, while others fear what might become of its chemical weapons stockpile.

Not all observers agree it's the beginning of the endgame for al-Assad, but all are sure there's no clear road map for what lies ahead.

The prospects for al-Assad are "very grim," said Shashank Joshi, an associate fellow at the UK-based Royal United Services Institute think tank and a doctoral student at Harvard University.

"There's no going back," he said. "He's not far from collapse, because what's occurred through defection or assassination is that the political part of his regime has been hollowed out."

By contrast Dr. Dan Plesch, director of the Centre for International Studies and Diplomacy at the School of Oriental and African Studies in London, considers it too soon to write al-Assad out of the picture.

But in a scenario where he is pushed out -- bringing to an end four decades of rule by him and his father before him -- the Syrian military will likely play a major role in what happens next, Plesch said.

Recent defections of high-level officers -- notably regime insider Brig. Gen. Manaf Tlas -- on top of the desertion of many rank and file personnel, signal an erosion of the army's coherence in the face of the rebellion.

Many of those at the top are determined to fight on to the end because they fear the personal consequences for them if they lose, analysts say.

In what some saw as a turning point after more than 16 months of violence, al-Assad lost four top aides following an explosion in Damascus last week, as rebel forces attacked the capital and Syria's commercial hub, Aleppo.

So far, al-Assad has shown no signs of quitting. But what's not yet clear is how much stomach he has for a continued bloody conflict, and whether he might be more inclined to negotiate a transition than some of his immediate entourage, Plesch said.

If al-Assad's ouster were the result of a "palace coup," involving negotiation between some insiders and the insurgency, slightly more continuity would ensue, said Joshi. However, such a transition is likely to be unstable because many rebels would refuse to accept it and would fight on.

He believes it more likely that the regime collapses entirely and the Syrian National Council -- an opposition coalition whose leadership resides outside of Syria -- stakes a claim to lead the transition as part of a coalition also involving opposition figures within Syria and Kurdish and liberal representatives.

However, unlike Libya, where the National Transitional Council presented a fairly unified voice as Gadhafi's regime crumbled, the opposition in Syria remains more fragmented and no credible transitional leader has yet come to the fore, Joshi said.

Plesch agrees that while the Syrian National Council "aspires to be the linchpin in the transition," questions remain over how effective it could be and what support it commands among rebels on the ground.

Ausama Monajed, who advised a previous president of the Syrian National Council, told CNN in March that his group has a plan for a post-Assad era, including the formation of a transitional unity government and a body to draw up a new constitution and election laws, leading eventually to parliamentary and presidential elections.

At the time, observers responded with skepticism. "There's a lack of coordination amongst the insiders, and they represent the outsiders, not the insiders," said former U.S. ambassador to Syria Edward Djerejian. "It's not a coherent opposition leadership."

Another scenario sees Syria descend into a chaotic and bloody sectarian conflict, pitting Syria's majority Sunni Muslims against the ruling Alawite sect, an offshoot of Shiite Islam, and embroiling its Christian, Druze and other minority groups too. Such a conflict risks destabilizing the wider region.

The recent defection of two key Sunni figures, Tlas and Syria's ambassador to Iraq, Nawaf Fares, means all al-Assad has left is a narrow Alawite bloc with shrinking public support, Joshi said.

If the regime collapses, the Alawites could retreat to strongholds in the northwest of the country around Latakia and attempt to reconstitute a state there, he said. Syria's Kurds could also seek greater autonomy, a move which would worry Turkey, which has a troubled relationship with its own Kurdish population.