I have in front of me a report from 2005 by the very scientists that are currently studying this eruption. This is a risk assessment of probability of eruptions and subsequent flooding (which is the major threat). I have property on the outskirts of the most extreme flooding area.
I could post the article here, but it is in Icelandic so it is only of use to few people.
Eyjafjallajökull is known to have erupted 4 times in the last 1500 yrs (~500, ~920, 1612 and 1821. Katla is known (and estimated) to have erupted about 25 times since ~700 (this includes possible minor eruptions that never made it through the glacier). Of this number, 6 are considered to have been major. The interval between major eruptions 150-300 years. The last major one was in 1918.
Eyjafjallajokull and Katla have erupted at a similar time 3 times, but the only time it is known Katla was following was in 1823. It is apparently not documented which went first in ~920 and 1612.
So hold your southern horses for a while. Everything moves around here, and does so all the time. We are pretty used to it. I have watched and flown around about 8 eruption in my aviation life. We even used to do sightseeing flights around the eruption.
Prof.Haraldur Sigurdsson who was on 60 minutes recently, and is renowned around the world of volcanology considers this Katla angle "a media fever". Is that where you are from? Your profile certainly does not indicate that you are an aviation professional.
The thing is that this is the first sizeable eruption in this part of the world since the start of modern aviation. Todays aviation industry needs to learn (and fast) how to live with it, and get as close to normalcy as possible.
Oh and yes the eruption was spectacular to watch on Friday and Saturday this weekend from my country property, 30 miles from the crater.