[Update]: Turns out soon is a lot sooner than I expected - the PTR patch is now live!
Despite the use of test servers being pretty common across all Blizzard games, they are mostly used to double check balance changes the developers locked down weeks prior. However, the upcoming Overwatch PTR (Public Test Realm) is going to be something completely different.
Instead of simply offering up complete changes to test for bugs and broken interactions, the Overwatch team will be putting out some highly experimental balance changes in order to see what works, what doesn't, and what requires some tweaking before its ready to see the light of day. If this sounds like something you might be interested in, here's the full announcement from Designer Geoff Goodman:
I wanted to drop in and talk about our upcoming PTR patch that is due out very soon. We are going to try something a little different this time, so you might be surprised when you see the patch notes for it.
Previously we've been using the PTR, first and foremost, to make sure the game is solid and there aren't any heinous issues that would prevent us from releasing the patch. There was a nice secondary goal of gathering feedback on any changes we're planning and trying to iterate on them quickly, but we didn't always have time to try multiple different iterations of any particular change.
This time around, the PTR is likely to be around a bit longer than before, so we're taking this opportunity to try out some more significant hero changes, and the push more significant iterations throughout this PTR cycle.
The PTR patch changes you guys see are unlikely to make it through PTR unchanged, unlike previous PTR cycles.
We want to try a bunch of things and see whats fun and working, and iterate more quickly from there. In this way, we get to have you guys involved earlier in the process.
One quick note, since I already know this will come up. There aren't any Symmetra changes for this patch. Her changes ended up being much more significant and require more time to finish up, but shes feeling pretty great internally so hopefully we can get her out there pretty soon."
What exactly this patch will entail, nobody outside of Blizzard really knows, but I have a feeling its going to be a couple of changes to hopefully address the extremely popular and effective Nano Boost + Death Blossom combo. Neither ability is really overpowered on its own, and nerfing them would have a lot of unintended consequences to Overwatch as a whole, so this sounds like the perfect issue to tackle with a highly experimental test server.
There is currently no exact ETA on when this PTR update will land, but Goodman has stated that it will most likely be later this week. And best of all, he has expressed interest in awarding players with loot boxes, so chances are you won't be losing out on all those sweet Halloween items while doing something that helps Blizzard and the game as a whole. I'm afraid this little addition hasn't been confirmed just yet, but it is still good to know that Blizzard is well aware of the problem!