I'm not surprised by that, as I'm pretty sure that was always the intention.
What little communication there was about this, even within Mozilla, seems to have been miscommunication.
AlfonsoML wrote:On the other side... goodbye to themes. Not a single word that denies this fact.
Like I've already said, I seriously doubt that there will be any significant changes to themes until there is a comparable replacement available.
In my skimming of some of the discussions, I've seen comments about making traditional themes act more like extensions (as they kind of already are), then continuing to develop Personas as a lightweight replacement (adding the ability to change icons, etc...). Overall, this is probably a good direction to move in, but as the developers have pointed out, there is still a lot of work needed.
But as aaron has pointed out, there are extensions available that allow for more extensive themeing than Personas (and from the sounds of it, easier and more robust than traditional themes)... So theming is not in danger of disappearing.
There have always been ghosts in the machine... random segments of code that have grouped together to form unexpected protocols. Unanticipated, these free radicals engender questions of free will, creativity, and even the nature of what we might call the soul...