Nick Studios was only filming Slime Time Live over the last three years. They stopped last year, and now all of Nickelodean's productions are shot in either California or New York. The Nick soundstage was most recently used for Halloween Horror Nights to hold one of the houses, but no future plans have been announced. It's big enough that hopefully they will put a real attraction in there.
I don't see them installing another attraction in there... NBC is really trying to utilize the whole studio aspect of this park and is trying to get a few shows shot there... currently TNA Wrestling (Spike TV) is shot there on a weekly basis as well as a few things for Sunshine Network... they recently shot a pilot for a talk show and Ellen Degeneres' producers have been to the park numorous times scouting it out... I think we'll see a TV show there before we see an attraction... even the production website lists it as being available for rental...
During HHN they had a haunted house (Where Evil Hides) and wardrobe/make-up in there... before that they still had the Omac puppet from Legends of the Hidden Temple but it's gone now
A few other companies located on the backlot include Pink Sneakers Productions who are famous for their MTV/VH1 shows, most recently Hulk Hogan Knows Best and True Life... Lightship Entertainment is also located on property and you probably recognize the name from the recent Disney Xmas Parade tapings and from their TLC shows about the parks...