I cannot be sure how reliable or serious the comment is right now, but suspect that if that becomes the official line, it'll be a problem for a lot of the users (and thus for Salesforce itself). To be able to retire an existing tool means its functionality can be better replaced by a new tool, or the functionality is simply no longer needed. I don't think anyone can claim the latter yet, so let's examine whether Developer Console can fulfill the former:
- Is there a good option for hooking up to source management?
- Is there a good option for managing deployment process?
- Is there a good option to quickly switch org/environment?
Once you contemplate the answers for these questions, it's not hard to draw a conclusion. And I'm sure there's other questions too.
The Tooling API would be a good start for an era of some great alternatives to Force.com IDE. But we're there yet. Things like Sublime Text2/MavensMate alone won't get us there.
Contrary to the size and adoption might have indicated, SFDC sometimes still doesn't think as an enterprise platform should. I hope the discussion on the Force.com IDE was among moments like that.