UPDATE 14TH NOVEMBER: New hero Ashe is now live on all platforms - PC, PS4 and Xbox One. Along with Ashe come balance changes and bug fixes. Roadhog has had a fair bit of work with the intention of making his abilities more consistent, particularly his hook; and Reaper, Mercy and Symmetra have all been slightly buffed. Full Overwatch patch notes are on the official forum.
ORIGINAL STORY 6TH NOVEMBER: New Overwatch hero Ashe is available to try on the PC Public Test Region now. To use the PTR, load your Blizzard/Battle.net launcher and select, from the Region/Account dropdown above Overwatch's Play button, the Public Test Region.
Ashe was unveiled at BlizzCon 2018. She's the leader of the Deadlock Gang McCree used to run with before he left to join Overwatch's covert ops department Blackwatch. McCree and Ashe have history.
Ashe is a gunslinger of sorts, packing a repeater rifle rather than six-shooter like McCree. She's the first Overwatch character to be able to aim down sights and she reloads per bullet rather than per clip. Ashe also packs dynamite she can leave to either explode on the floor or detonate mid-air with a shot.
But it's Ashe's Ultimate which draws the eye. Ashe, a rich girl turned rebel, summons her lifelong AI butler/pal Bob to attack enemies. Bob charges in a straight line and uppercuts the first enemy he comes across - or group of enemies - into the air. He then behaves like a well-armoured turret, automatically shooting enemies nearby. Apparently he's devastating if nano-boosted by Anna - Jeff Kaplan told me that during my Overwatch BlizzCon 2018 interview.
When Ashe will be released on Overwatch's public servers, and consoles, isn't known. She'll presumably need a couple of weeks' testing first.