Blizzard hasn’t given specifics on how either character will be implemented within the game yet. But remember that Junkrat is a defensive player within Overwatch, whose attacks deal splash damage galore.
Ana is a support character who should dole out healing when she arrives to HotS. The two characters will join other hero skins including Commandant Varian, Destroyer D.Va and Shrike Ana. They’ll play on the new map Volskaya Foundry.
The new heroes will likely hit the public test realm sometime before the main game but Blizzard has given no specific timeline yet.