Strongly depends on the last races they add when the game releases.

A Dragonborn Druid if all PHB races are added.

A Half-Orc Druid (Possible Barbarian multi-class) if they decide the reptile head is too complicated.

A Lizardfolk Druid if my wildest dreams come true.

The Dragonborn is a traveling scholar who believes creatures born of magic chicanery are still living things and thus deserve his Circle's protection, so he aspires to create a refuge for the unnatural living things of the world to live freely and safely.

The Half-Orc is the product of an illicit affair between his noble adventurer mother and an orcish warlord she fell in love with. He ended up living on the streets after his mother passed away, but was picked up and trained by his mom's old adventuring companion; a halfling druid.

The Lizardfolk is a servant of a Green Dragon that rules over his tribe. He was sent out to become an adventurer by his dragon-god so that he could accumulate wealth and bring it back to enrich his hoard, as well as bring back information about the wider world.