Having heard a good talk about this from MIT, I wanted to go back to this question. Part of the reason they went with M87's black hole first is due to the gas and dust issue I mentioned, but there's a bigger issue...
Before they took this image, we had some measurements of how wast gas, dust, and stars were moving around these black holes. Things around M87's black hole move a little more slowly. We expect visible changes in the image to take a couple of weeks - which means that if each observation takes a day, the image is mostly static for that period of time.
Things are moving much more quickly around SagA*, and we expect the image to change over the course of days or even hours, which means that the day-long observations used would yield very blurry images. They are planning some upgrades to the system that should help with that for the SagA* observations, but they could look at M87 without them.
Thanks for the followup and for taking the time to answer these kinds of questions.
Since M87 is very far away, we're looking at how it used to be. What do you imagine it looks like now? Did everything get sucked into it? Or did life go on and everybody there is used to the big dark spot in the sky?