I think the Specialty/Feat system offers and excellent delivery method for the wild shape mechanic. Since Next is all about choice and scaling, that would allow druid players the option to skip Wildshape if they don't care for it as well as give other nature-y characters the opportunity to pick it up. It seems like it would be pretty easy to implement.
I think the prerequisite should be the ability to cast primal spells. Yes, I think that primal spells should be codified into Next, but that's a different conversation.
The first level of the Specialty would probably just add some sort of enhanced animal empathy/affinity, but from level 3 on the character would gain the ability to change into a natural beast as an action. I don't like per day abilities, so I'd be more inclined to just have realistic limitations on the character's abilities while shifted. As far as statistics and abilities, I'd think it would work somewhere between 4e sentinel companions, 13th Age companions, and the familiar rules in the playtest. So, like... there would be a set of base assumptions that would be modified by an animal affinity the druid chooses. A bear would be tougher, a wolf stronger, etc... probably scaling with level somehow.
From level 6 and onward, levels would offer the option to add more affinities and/or expand the character's abilities while shifted. Things like adding the ability to speak/cast/heal while shifted and such.
I think it's pretty exciting and fun to think about Wildshape rangers and shaman in addition to druids. This really plays into the Next design philosophy as it would give players the opportunity to really theme a Nature-based character without complicated multiclassing and such.