I wish I would only receive 'english' announcements by e-mail xD.
I think for Etray the fake transparency was truly needed, otherwise icons in a small box at the screen corner would have looked horrible. So fake transparency did the trick.
Now that we won't need it, you say the only app left using this is the terminal. My belief is that... users with more powerful computers could turn compositing on in the near future, once we include this "compiz for E" thingy xP forgot it's name, so we could have real transparency. If you have a low end computer, you might not want a slowing down plugin to make your terminal transparent. And to be honest, fake transparency only works for stuff ON the desktop... if you place it over a window, it will still blend with the wallpaper so =P at this point I think it's senseless.
Yah, we don't need it >.< that's my personal belief. This would be just holding on to old technologies. Though you might wait to remove this until they get the chance to use real compositing, so they can choose.