In "Single All the Way", it looks like Kermit and Piggy will eventually get back together. Since this happened, I had suspected they would be the end of the season, but now I'm thinking that maybe it'd be better if the relationship were like on The Muppet Show, where it was usually one-sided.
On TMS, it was usually one-sided, though Kermit sometimes did a romantic number with Piggy (we never saw any backstage happenings leading to such moments to show why Kermit did the numbers) and was sometimes jealous of male guest stars she showed an affection to (but not all male guests; he wasn't jealous of Jim Nabors, Charles Aznavour, or Elton John).
Then in most of the movies and specials it wasn't one-sided, or at least wasn't so easy to tell. They do a lot of bickering in The Fantastic Miss Piggy Show, but I'm not sure if that's a "couples bickering" or a "she love shim, he doesn't" bickering.
On The Jim Henson Hour and Muppets Tonight, they weren't shown "together or not" very often. Piggy only appeared once on JHH, and in that episode Vicki made a comment that Piggy dumped Kermit. On MT, there's hardly any scenes where they are a couple or where Piggy mentions/shows her love for Kermit, with the most major of the rare instances being presented as a flashback from the 1980s.
But while it may have been less one-sided in the movies and TV shows, it seems like it was often one-sided in interviews and appearances, with Kermit saying that the ending of The Muppets Take Manhattan was just a movie (and in an interview for Good Morning America, he said that The Muppet Christmas Carol was only a movie; I remember seeing this as a kid and being confused by Kermit's comment that they weren't really married, since I thought they really did marry in MTM). And yet since 2011, it seems like the relationship was no longer one-sided, even in interviews, until the break-up was announced last year.