Google maintains a nice page that displays the current distribution of Android versions in the wild. Here are the charts as right now.
That increasing share of 2.0 or greater is likely due to new phones coming out, rather than users of previous versions abandoning their devices.
Obviously, I'm chomping at the bit for not only new devices to come out, but the older ones to be upgraded. There were rumors that the myTouch was going to get 2.1 in June, which obviously didn't happen. Hopefully that will happen this month, since they represent well over a million potential users of WordWise.
Meanwhile, it looks like Droid users are the dominant demographic for WordWise, clocking in at just about 50% of our users. The Evo and the Eris both clock in around 10%. Here's hoping that as many older devices as possible get upgraded.