That's for a reason. Why not 3.5?
- the issue is being reported since 1.5 days [#22495](http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=22495), 
- there are no known backward compatibility issues

Is it that deprecating is scheduled for 4.0?

Should the comment look like that then?
```PHP
/*
 * @deprecated  4.0  Use JResponse::setHeader() instead
 */
```