According to the rumor mill, the Slaughterhouse appearance during Em's verse in the "Forever" video was no coincidence. Apparently the lyrical super group is in negotiations with Shady Records. More info (and background) can be found on Miss Info's page.
I think this would be a great move for both parties.
This looks like a screen grab of Em's part of the "Forever" video. It was spotted over at Rap Radar (as if the Giant black & yellow logo didn't give it away). The Video Premieres on 106 & Park Today! Looks like Slaughterhouse in the background.