Baptiste is going to be added in Blizzard's update for Overwatch on 19 March 2019 and a pile of heroes with mobility and armour will get a balance pass. Mobility is mostly buffed, while armour is nerfed against beam weapons and DoTs.
Damage over time effects such as Ashe's Dynamite and Moira's Biotic Orb will now strictly deal 20 per cent reduced damage against armour instead of the old calculation, which is effectively a nerf for the high-tech tanks like Reinhardt, D.Va and Orisa. The same damage calculation will apply to beam weapons so Symmetra and Zarya will have an easier time melting said tanks.
Mobility will be buffed, nerfed and altered in other ways in the update. Doomfist will have lower cooldowns on his totally-not-Shoryuken and Seismic Slam, Orisa's speed while shooting her weapon will be decreased by 30 per cent instead of being halved and Soldier 76 will have a lower delay between Sprinting and using his Pulse Rifle.
Meanwhile, one of the most mobile heroes in Overwatch, Lucio, is getting the nerf bat. Amp It Up will boost movement speed by 50 per cent instead of 70 and Crossfade's default speed boost will be 20 per cent instead of 30. On the other hand, his wall-running will provide a 40 per cent speed buff instead of 20. Calling it right now, this is going to be a mess during Control Point overtime.
While technically a matter of mobility, the flight mechanic alterations are both a nerf to those who can fly and a buff for those with knockbacks. D.Va, Mercy and Pharah can now be knocked back and slowed while flying so expect Mercy's revives to be interrupted if she is under Valkyrie's effects. You can also boop D.Va if she's charging towards you.
Unrelated to mobility or armour, Widowmaker is getting a major change to her ultimate. Infra-Sight will now show the enemy targets' health bars which is a great advantage when taking pot shots but the effect will cease if she dies before Infra-Sight wears off.