Ya never know, it has done some impressive eruptions previously and has been fairly active but not quite a krakatoa is likely here, I could be wrong tho. :)
An elderly resident of the slopes of Mount Merapi is given a health check at a refugee camp in Sleman. The alert status of Indonesia's Mount Merapi volcano has been upgraded to its highest level, an official said, meaning some 34,000 people living in its danger zone face mandatory evacuation.(AFP/File/Bay Ismoyo)
Most likely a Pinatubo scale eruption is all we should expect, at most. Pinatubo brought Alaska a nine-month winter and record snowfall, perhaps some global cooling for a couple of years.