I use the word panel because I also need the option to run a bottom panel like firebug does/dev tools does. A side bar sounds as an element that is display in either the right or left side. I would like to see either one API for left/right and top/bottom panels or bars. Or just horizontal and vertical panels/bars.
I read trough the discussion in the linked bug and it worries me a bit that it is discussed to fix the side bar on either the right or the left side or to always display it with no show/hide option from a toolbar button. Also there is no mention of a horizontal panel that I rely on in my add-on. Actually I show both a left side bar and a bottom panel at the same time. It seems that this will not be possible. I fear that the API will be much to limited comparing to the options available for overlay add-ons.