I'm due to do a transit late next month as well. As SanDiego1K says, there is near zero chance of risk if you're just in transit. I mean, whats the probability that the airport will be attacked within the hour and a half that you (or me) are there doing a transit?

I'm not one to take uncalculated risks, and I would have gone ahead with a visit to Colombo (ie. into town) even in the current situation. Of course, I'm the kind of person who regularly flew into HKG during SARS and BKK during the bird flu outbreak.

Don't let the media put you off, but do keep up with whats going on there, so that you can cancel your trip upto the point before you fly out if it worsens.