Like everyone else here, I did like Midna a lot as a character, but it seems unlikely that her re-occurrence will fit with the story. However, I will say that they could make a story in which her appearance fits.
Perhaps the most likely reappearance of her is in a flashback, like the one in Majora's Mask where Link remembers Zelda and the Song of Time. This would only work in a direct sequel to Twilight Princess.
Another possible way of seeing her again is time travel, but I don't see that returning to Zelda any time soon. Time travel in Zelda seems like it should be something specific to the Hero of Time, relating to his title.
The last possible way for us to see Midna herself is for, in the story, another way into the Twilight Realm to be revealed or opened. This could very well happen in the same game as the flashback involving Midna. When Link and Midna meet again in this situation, we would see her in her original(story-wise) form, not the imp form that she's well known as.
I also know another thing that could and very well might happen: another character with similar design to Midna could appear. This character could be similar to either form and perhaps also have a similar personality or voice, or maybe just the latter and not the former.