Is Pluto a "proto-planet"?
Pluto will never be a planet.

There are a number of technical papers that give more precise meaning to the concept of "clearing the neighborhood". It's not just now, it's can the object in question clear the neighborhood of its path while the Sun is still a star.

In the case of Pluto, Ceres, Eris, and a host of other not-quite-planet objects, that will not happen. Ever. Or at least so long as the Sun shines. After that, does it matter?