It was more a joke than anything, haha :]There's no chance that Jigglypuff will not appear in this game. Only question imo is if it'll still keep sing or if it'll get something new and / or Fairy-typed. It'd also be interesting if Competitive could be implemented somehow into its design (though frankly how to do that without making it lucario is beyond me).
Though I would really like to see Sing replaced if Jiggly did make a return. Maybe with something like Dazzling Gleam, in which a ray of some sort shoots upward? Idk haha.