Overwatch's least-played hero is undergoing a major rework in the PTR, and everyone is wondering when we'll get the official release of the new and improved(?) Symmetra. Many speculated that her changes would go live in time with the transition to competitive Season 3.
Unfortunately, as game director Jeff Kaplan just confirmed via the Overwatch forums, Symmetra's rework will take "a bit" longer before being fully available.
This leaves the next logical choice for a timely release of the new Symmetra as coinciding with the still-unannounced Christmas/Winter Holidy event, although it is possible for them to simply release her when she's ready regardless of timing.
It will be strange for Symmetra to be completely reworked mid-season, potentially shaking up the competitive scene while it's still going on, so this could indicate that more big changes are coming to the hero.
Whether or not her rework was effective in making her a viable pick in all situations is still up in the air, with many people feeling that her alternate ultimate ability was not effective enough. We will see once she is released to the public, but that doesn't seem to be happening any time soon.