I'm marking this status-completed, since for a *handful* of badges it is implemented:

[![review badge progress][1]](http://stackoverflow.com/review)

There are a few others like this - Fanatic progress [shows up on your  user profile](https://meta.stackexchange.com/questions/865/consecutive-day-count-in-profile), [Research Assistant][2] on tag wiki pages, etc. 

That said, I don't see it ever being implemented *across the board* - consider a badge like [Unsung Hero][3], where you might well qualify for long enough to earn the badge, only to finally collect some up-votes on those answers. Even badges like Tumbleweed are problematic, since you might easily be 90% of the way there only to gain a few votes or attract a few views and suddenly be back at 0%. 

In the end, not all badges are equal; some are milestones you might strive to reach, others are consolation prizes or recognition for truly exceptional efforts, contributions, or plain old good fortune. Displaying progress where there's something you *should* strive to progress in is great, but a few surprises are nice here and there too. 


  [1]: https://i.sstatic.net/i7kd1.png
  [2]: http://stackoverflow.com/badges/1656/research-assistant
  [3]: http://stackoverflow.com/badges/226/unsung-hero