As this article says wish can be used in informal speech in the continuous tense, which was done in the 15th episode of the 5th season of the TV show Friends. Here is the excerpt:
Monica: (kneels with him) Chandler, umm, I want you to take just a minute and I want you to think about how ridiculous this sounds.
Chandler: Yeah, I'm kinda wishing everyone wasn't here right now.
How would the meaning of the sentence change if Chandler said I wish instead of I am wishing?