No one at this stage what type of eruption may (or may not) occur. Pyroclastic flows, ash, lava?
Evidently the 1963 eruption lasted for a year, but as we in New Zealand know, just because a volcano is in a state of eruption does not mean that it is hazardous to a wide area. It is an ash cloud that is hazardous to air traffic, but often air traffic can be safely routed around the cloud - just has occurred here in New Zealand with Ruapehu and Tongariro. Pyroclastic flows are very hazardous, but the distance they can travel isn’t so great - this will be one of the deciding factors in the current evacuation zones.
Until Agung's eruption really gets underway I don’t think anyone knows what will happen and even then trying to predict how long it will last? Again it’s a case of wait and see.
I just hope that it doesn’t go on for too long and that people stay safe and a minimum of damage is done to the diving areas close to Gunung Agung - afterall the 1963 eruption put the Liberty in the water where she is now