Maybe. But to me it would need to be part of a large bunch of classes and subclasses all dealing with the theme, like the psionic classes/subclasses being made do. And you need to have a setting for which planeswalking is an actual thing that PCs will do starting at 1st level.
Psionics are going to be made as part of the eventual Dark Sun setting 5E document, because psionics are an intricate part of Dark Sun. Likewise, I wouldn't see a planeswalker class (and further subclasses) until we probably saw a Planescape or Spelljammer setting 5E document, since those are the only settings where actually going from plane to plane from the very beginning of your adventuring career is a part of it.
There's no point in a planeswalker class for a Forgotten Realms character for example, because that's a setting where you won't actually go to other planes until you most likely start hitting Tier 3 at 11th level. So having it in the base game is not particularly necessary.