Well, like usual Macromedia (er.... Adobe) is really lagging on getting the specs out. From what I understand, Macromedia was really disorganized in regards to the SWF spec even internally, so it shouldn't be suprising that it takes forever to get this stuff out to everyone else. In the mean time, go visit:
And you can get some info on the current tags. It's a wiki, so feel free to add your own input if you know a bit more or figure out anything that isn't listed.